In 1690 the Spanish gave the name "San Francisco" to this 62-mile Brazos River tributary; but on an 1822 map, Stephen F. Austin, "Father of Texas", marked it "Yegua", Spanish for "mare". Mustang mares and foals then grazed among the Indians on the timbered creek. In 1826, colonist John P. Coles built a mill on the stream. A measure signed in 1837 by Texas President Sam Houston made the Yegua a county boundary. Floods often devastated the area until Lake Somerville harnessed Yegua's waters in 1967. Now a recreation area, the lake and creek benefit crops, wild life, and vacationers.