Girl Scout Cookies are cookies sold by the American Girl Scouts to raise money for their activities. $700 million worth are sold a year (as of 2010.)
The cookies are made commercially for them. There are two authorized makers of the cookies as of 2010: ABC/Interbake and Little Brownie Bakers.
Each Girl Scout company must offer at least the three following flavours of cookies for sale: Thin Mint, Peanut Butter Sandwich (aka Do-Si-Dos) and Shortbread Trefoils.
Other flavours include: Caramel deLites (aka Samoas), Peanut Butter Patties (aka Tagalongs), Thank U Berry Munch (introduced 2010), Lemonades, Dulce de Leche, Lemon Chalet Cremes, Thanks-A-Lot, and Daisy Go Rounds.
In addition to the three mandatory flavours, a baker can make up to 5 of the flavours above, for a total of 8 kinds. Not all of the optional flavours are available in all areas.
The cookies are sold in boxes, by weight. Consequently, the size and number of cookies in a box will vary, depending upon which variety of cookie is being bought.
The most popular flavour is the Thin Mint.
Girl Scouts in America started reducing trans fats in their cookies in 2006. By 2009, they had reduced trans fats to .5 g per serving, which met the FDA qualifications to call them “zero trans fat.”
The cookies are also kosher.
The Girl Scout, aka Girl Guide, movement in America was Juliette Low (1860 – 1927.) She was married to an Englishman, who had died in 1905. She divided her time between England and the States. She had worked as a Girl Guide leader for troops in Scotland and London.
In early 1912, she was on a ship to America with Lord Baden-Powell and his future wife, Olave Soames, and they discussed ideas for establishing Girl Guides in America. Later that year, on 12th March, she registered the first troop of American Girl Guides. There were 18 girls in the troop.
Later the next year, the name was changed in America to Girl Scouts.
Girl Guides First Sell Cookies to Raise Money 1917 / 1918
Reputedly, the first mention of Girl Scouts selling cookies to raise money is that of the Mistletoe Troop in Muskogee, Oklahoma in December 1917 at their high school cafeteria as a service project to raise funds for troop activities. Sadly, a search of all Oklahoma newspapers by CooksInfo.com from 1917 to 1919 has failed to turn up an exact record of this.
What we can state for sure is that there is a reference to a Girl Scout troop, named the Mistletoe Troop, selling cookies to raise money sometime between October 1917 and April 1918 — and that the cookies referred to were wheatless.
The Mistletoe Girl Scout Troop was formed in October 1917 at Central High School in Muskogee, Oklahoma, by two gym teachers there, a Miss Marion Brown and a Miss Aileen Stroud, who lived together on a duck farm just outside the city.
In November 1917, the school began observing the requests of the American Food Administration to hold Meatless Tuesdays and Wheatless Wednesdays, to help the war effort. 
The next month, in December, the students at Central High School had an unexpected break from school, as did those in most other Muskogee schools, as the local gas company wasn’t able to supply enough gas to meet the demand that a cold snap had caused. The school was closed from 6 December 1917 to 7 January 1918 on account of this, with the temperature of some of the school’s rooms barely reaching 50 F (10 C.) 
We have found a record of the Mistletoe Troop sending a box of gifts to soldiers at Camp Bowie in central Texas, which had been hard hit by pneumonia, killing many of the soldiers there:
“The Mistletoe troop, girl scouts, sent a large box of Christmas packages to Camp Bowie this morning from the Red Cross headquarters.” — Women in War Work column. Muskogee Times Democrat. Muskogee, Oklahoma. 17 December 1912. Page 5, Column 2.
The following excerpt is where we learn who organized the troop, where they lived, what activities the girls did in their first 6 months as a troop — and that some of the girls made wheatless cookies to sell to make money for the Girl Scouts. So, it may well be that the first cookies sold by Girl Scouts to raise money were in fact wheatless. Note, however, that we can’t tell what month exactly this was done in, so there’s no solid backing for the December 1917 date in a school cafeteria — especially with the school being closed almost all of December.
“One of the most patriotic organizations in Muskogee is that one known as the Girl Scouts, which was organized at Central High School last October by Miss Marion Brown, gym teacher. This organization is the Mistletoe troop of the national organization of girl scouts with Miss Marian Brown as captain and Miss Aileen Stroud as lieutenant. [Ed: her name is spelt variously as Marian and Marion.]
Everything that these girl scouts do is patriotic. The organization is strictly a patriotic affair. At Christmas time, they made Christmas packages for the boys from Muskogee at Camp Bowie. Later in the year, the girls gave a circus in the gymnasium of the high school and cleared $57 with which they purchased two large tents. Every cent that the girls spend for the organization, they make. They are not allowed to bring money from home. Some make wheatless cookies and sell them, others do different similar things just as patriotic. At a farm, south of town, which is know as the “mallard duck farm,” Misses Brown and Stroud live. At this farm, the girls have a war garden. They have an early crop which will be ready for sale soon. Then they will plant a later crop. From the sale of these vegetables, they will buy implements for the farm and later in the summer the girls will buy uniforms. Every week end finds a large crowd of the scouts out at this farm for the week end. With the two large tents they have, twelve can stay at a time.” — Girl Scouts have great fun at duck farm; also, they’re raising war garden as “bit.” Muskogee Times Democrat. Muskogee, Oklahoma. 27 April 1918. Page 13. Column 5.
Sadly, both the leaders, Brown and Stroud became ill together in December 1918 during the second wave of the 1918 flu epidemic, which hit the whole town of Muskogee hard. Brown did not survive the illness.
“Central High School suffered a great loss last week in the death of Miss Marian D. Brown, director of physical education for girls. Miss Brown came to the work four years ago, after graduating from the New Haven School of Gymnastics, and from the first entered whole-heartedly into the school life of the girls of Central high school. She soon became the friend and confidant of the girls in her immediate classes, and with the assistance of others of the faculty, organized the Girl Scouts and the Rousseau club. For a time these organizations maintained a home in the outskirts of the city, where the members cultivated war-gardens and received outdoor exercise. …. Miss Stroud returned to her duties as physical culture instructor on Wednesday.” — “News of the Schools” column. In: Muskogee Daily Phoenix. Muskogee, Oklahoma. 8 December 1918. Page 6. Column 2.
Stroud carried on leading the Girl Scouts:
“Under the direction of Miss Aileen Stroud, director of physical training at Central High school, the girl scouts are going to give an exciting circus. There’s going to be snake charmers , hot-dog stands, and everything that goes to make up a good circus.” – “High School Girl Scouts To Give Circus March 21.” Muskogee Times Democrat. Muskogee, Oklahoma. 17 March 1919. Page 1.
Girl Guide Cookies for fundraising gains national backing: 1922
By 1922, the idea of selling cookies as a fund raiser had started to gain some popularity. The Girl Scouts had a national magazine by this time, called “The American Girl.” They ran in it a cookie recipe by Florence E. Neil, a Chicago director for the Girl Scouts. They suggested using this recipe for cookies; the estimated cost of making the recipe was 26 to 36 cents for 7 dozen cookies, and they felt that troops could sell the cookies for 25 or 30 cents a dozen.
By 1923, the Girl Scouts were firmly associating themselves with cookies:
“A five foot bag of cookies baked by girl scouts was presented to Mrs. Coolidge, wife of the president, who has accepted the honorary presidency of the organization. The cookies were presented by a group of Washington girl scouts headed by Mrs. Percy H. Williams of New York, member of the national executive board, and the wife of the president, authorized the following statement:
“It is with great pleasure that Mrs. Coolidge accepts the invitation to become honorary president of the girl scouts. She is very heartily in sympathy with all its aims and feels that it is doing a great work in training the girlhood of America in the highest ideas.” — “Mrs. Coolidge Given Bag of Cookies by Girl Scouts. Associated Press. In “The Bridgeport Telegraph.” Bridgeport, Connecticut. 18 October 1923. Page 3. Column 3.
In November 1923, the Girl Scouts of Portsmouth, New Hampshire held a cookie bake sale with the backing of local businesses. Note the mention of a National Cookie Day — 3 November. In the following passages, we also learn the exact recipe that was issued by the National Girl Scouts back in 1922:
“The Girl Scouts of Portsmouth and vicinity held a council meeting in Freeman’s Hall on Wednesday afternoon, Mrs. Louis Ewald, the commissioner, presiding. Plans were completed for the Girl Scouts entertainment to be given in Freeman’s Hall on Friday evening in recognition of Girl Scout Week. It was voted to observe “Cookie Day”, Nov. 3, a day having been chosen by the Girl Scouts throughout the country when they are to make and sell cookies. The local Scouts will also hold a food sale at that time and cookies will be made and baked in the windows of the Portsmouth Gas Company and Rockingham Light & Power Company’s window on Pleasant street, the use of both windows having been given the Scouts for this purpose.” — “Girl Scouts Plan for ‘Cookie’ Day.” Portsmouth Herald. Portsmouth, New Hampshire. 25 October 1923. Page 4. Column 3.
“The local Girl Scouts will have a cookie sale this Saturday, exactly as held by the girls of Washington, DC recently, when Mrs President Calvin Coolidge helped them. Which cookies are the best, those from a gas stove or those from an electric stove? This can be decided Saturday from 2 until 6 pm for the Girl Scouts will cook cookies in the stores of the Portsmouth Gas Co. and the Rockingham G.L and P. Co. Buy your cookies both places and decide for yourself.”– Girl Scout Movement Strong Here. Portsmouth Herald. Portsmouth, New Hampshire. 2 November 1923. Page 8. Column 2.
Over 100 dozen sold here Saturday afternoon for the Benefit of the Organization – Girl Scout cookies were certainly popular in this city on Saturday and “Cookie Day” was observed by Girl Scouts all over the country, proved a big success in Portsmouth. Everyone was expected to eat a Girl Scout cookie, if not several, from the stock made and sold by the Scouts, who adopted a sale of that toothsome delicacy as a means of raising funds toward the maintenance of the organization. The cookies sold in this city by the Girl Scouts amounted to over 100 dozen and the demand exceeded the supply and 50 dozen more, at least, could easily have been sold.
The Rockingham Electric Light Company and the Portsmouth Gas Company gave the use of their office windows for the cause and aided in every way to help the committee in charge. The baking was done by electricity or gas, a stove being installed in each window for that purpose and the cookies were made in full view of the passers by and sold from 2 to 6 p.m. They were genuine Girl Scout cookies made by a recipe perfected and distributed throughout the movement by the National Girl Scout Council. This recipe is as follows:
One cup butter or substitute
One cup sugar
Two tablespoons milk
One teaspoon vanilla
Two and a quarter cups of flour
Two teaspoons baking powder
Cream butter and sugar, add eggs well beaten, then milk, flavouring, flour and baking powder. Leave dough on ice for 3 or 4 hours — overnight if possible — then roll thin and bake in quick oven. Sprinkle sugar on top.
…Girl Scouts in uniform were in both offices where the cookies were sold and were most enthusiastic over the sale. Home made cake was also sold, this having also been made by the Scouts.” — “Girl Scouts Cookie Day.” Portsmouth Herald. Portsmouth, New Hampshire. 5 November 1923. Page 7. Column 4.
In 1934, the Girl Scouts of Greater Philadelphia became the first council to sell commercially baked cookies. Keebler-Wyl baked 100,000 boxes of trefoil-shaped cookies for them to sell that December. It was a vanilla cookie.
In 1936, the national Girl Scout council asked Keebler-Wyl to produce their cookies nation wide. That year, from 24 October to 7th November, was their first official, nationwide fully organized cookie sales drive. By 1940, they had 14 authorized bakers for their cookies.
From 1942 to 1945, the Girl Scouts sold calendars instead of cookies owing to wartime shortages of baking materials such as wheat, sugar, fats, etc.
By 1951, they had 30 authorized bakers for their cookies.
By 2010, the number of authorized bakers had been reduced to two: ABC/Interbake and Little Brownie Bakers.
In 2010, some batches of the Lemon Chalet Creme Girl Scout cookies were reported to taste “off” by purchasers. The problem was caused by a breakdown in some of the oils being used. Customers were offered a coupon for a “Keebler free product.”
In 2011, the Duce De Leche and Thank U Berry Munch cookies were discontinued by “Little Brownie Bakers”. That meant areas served by them such as Atlanta, parts of California, New York City and Oklahoma would no longer have the cookies. Other regions in America, served by ABC Bakers, would still have access to those two flavours, as ABC planned to keep on making them.
Blake, Janet Cappiello. Girl Scout cookies pulled because of foul smell and taste. Associated Press. 26 February 2010.
United Press International. Girl Scouts trim cookie menu. 5 February 2011.
 The cafes and restaurants of Muskogee, as well as the cafeteria at Central High School, were practising Meatless Tuesdays and Wheatless Wednesdays [Restaurants Plan to Enforce Meatless Day in Muskogee Tuesday. Muskogee Times Democrat. Muskogee, Oklahoma. 5 November 1917. Page 2.
 “The Sawokia cafeteria and that at the Central High School were both observing the edicts of the food administration and not serving wheat breads on Wednesday.” –” Hot Cakes? Yes, Corn! No Wheat on Menu, Though.” Muskogee Times Democrat. Muskogee, Oklahoma. 31 October 1917. Page 1. Column 6.
 “The request for workers in the surgical dressings department has been answered well and it is hoped by those in charge that many more will offer their services. Several girls from the High school made surgical dressings this morning. When school was dismissed on account of the lack of heat, these girls came straight to the Red Cross rooms to work.” — “Women in War Work.”. Muskogee Times Democrat. Muskogee, Oklahoma. 6 December 1917. Page 5. Column 2
 “Continued cold weather with no material relief in the gas situation made it necessary, Tuesday, to dismiss even some of teh schools which up to that time had not sufference from the cold. Central High School was dismissed again at 10 o’clock Tuesday morning, after it had been found impossible to heat the building by using fuel oil in the furnaces.” — More Schools Closed by Cold. Muskogee Times Democrat. Muskogee, Oklahoma. 11 December 1917. Page 12. Column 5.
 “Central High School was still out Thursday and Superintendent Monroe said probably no attempt to hold school there would be made until Monday, as the heating of the building by fuel oil has proved entirely ineffective and has resulted in a boiler breakdown..” — “Mercury Down, Gas about Nil; Relief in Sight” In: Muskogee Times Democrat. Muskogee, Oklahoma. 13 December 1917. Page 7. Column 2.
 “All of which is by way of a reminder that Muskogee school children’s longest holiday vacation in years will come to an end, and the kids will begin their studies for the new year on Monday, January 7, according to a statement from Superintendent Monroe. The pupils will have had a full two weeks’ vacation when’ they return to their classrooms. Many of them were out even before the regular vacation began, due to the cold and gas shortage. Central High school students have been out more than three weeks. It is likely that the high school students win have to make up the week they missed just before Christmas by an extra week of school in June, although this has not vet been decided upon by the school board.” — “School vacation comes to close on next Monday.” Muskogee Times Democrat. Muskogee, Oklahoma. 3 January 1918. Page 8. Column 1.