These are floury potatoes, with a high enough starch content that they can also be processed commercially for starch.
They are now, though, mostly grown for farmers’ markets and by home gardeners.
Some like the flavour, to others it has no flavour.
It has a mealy texture when cooked.
Green Mountain Potatoes were developed by an Orson H. Alexander in Charlotte, Vermont in 1878 from a cross between Excelsior and Dunmore potatoes. A business directory for Charlotte / Chittenden County in 1882-1883 lists Alexander as: “originator and dealer in choice cereals and potatoes.” 
The potato was popular in Maine until the mid-1940s.
Green Mountain Potatoes are named after the mountains in Vermont.
 Gazetteer and Business Directory of Chittenden County, Vt. For 1882-83 Compiled and Published by Hamilton Child. Printed At The Journal Office, Syracuse, N. Y, August, 1882. Pages 262-273. Transcribed by Karima Allison ~ 2004.