The battle of San Patricio was fought in the streets of Old San Patricio at 3:00 A. M. on February 27, 1836. The general council of the provisional government of Texas had instructed Francis W. Johnson and Dr. James Grant to lead an independent military force against Matamoros, Mexico.

Although many of the troops left the command to follow Sam Houston, who opposed the expedition, about 60-70 men remained. Mexican general Jose Urrea, who learned of the plan from his network of spies, sent word to San Patricio settlers loyal to Mexico, instructing them to leave a light burning in their homes as a signal to mexican troops to spare them. After attacking a small force at Garza's Ranch (4 miles south), the mexicans struck San Patricio, killing 16 and taking 30 prisoners. Johnson, working late with a candle burning, and four others in his house escaped.

The Mexican troops then proceeded to Agua Dulce Creek (about 20 miles south) and attacked the remaining Texan forces under Grant's command on March 2. Grant and 11 others were killed, seven were captured, and six escaped. Together with those captured at Garza's Ranch and in San Patricio, they were imprisoned in Matamoros and remained in captivity until January 1837.