why is ther a alamo

It was the scene of a heroic stand by American troops vs Santa Anna's army who were trying to invade. Only one American survived the attack that went on for 16 days. "Remember the Alamo" became a war cry when the US later struck back. Davy Crockett was one of the American leaders who died there. So that's why.

Because if there wasn't an Alamo Texas may not have won independence from Mexico, thus eventually not joining the United States.

It's a reminder of those who chose Victory or Death. Freedom to the USA and Texas.