It comes from China and Indonesia, while cinnamon mostly comes from Ceylon.
Many North Americans have actually developed a taste preference for Cassia, as that is what they have been used to getting labelled as cinnamon.
Cassia cinnamon sticks are always preferable to real cinnamon sticks, as real ones quickly fall apart on you in hot liquids.
Cinnamon, nutmeg, allspice
The Romans and Greeks had cinnamon, but probably the variety they had was Cassia cinnamon.