When Davy Crockett went to Texas in 1835 McCulloch along with his brother Henry decided to go with him. They planned to meet Crockett at Nacogdoches on Christmas Day. The brothers arrived too late, however. McCulloch sent his brother Henry back home and went on to join Crockett at the Alamo in San Antonio. However, before reaching the Alamo, he came down with the measles. By the time he recovered, it was too late and the Alamo had fallen. McCulloch joined the Texas army under Sam Houston in its retreat to East Texas. At the Battle of San Jacinto (April 21, 1836) he commanded one of the cannons nicknamed the "Twin Sisters". At the end of the battle Houston found him and immediately promoted him to first lieutenant.