The , mission in San Antonio, Texas; site of a siege and massacre in 1836 (5)
I believe the answer is:
alamo
(Other definitions for alamo that I've seen before include "Where Davy Crockett died, 1836" , "Site of 1836 massacre in Texas" , "Famous battle in Texas launched by the Mexican army" , "The red planet" , "Texas fort, scene of famous siege by Mexican army" .)