Brazoria County is a county in the U.S. state of Texas. As of the 2020 census, the population of the county was 372,031. The county seat is Angleton.

The "Old Three Hundred" were 297 grantees who purchased 307 parcels of land from Stephen Fuller Austin in Mexican Texas. Each grantee was head of a household, or, in some cases, a partnership of unmarried men. Austin was an American approved in 1822 by Mexico as an empresario for this effort, after the nation had gained independence from Spain. By 1825 the colony had a population of 1,790, including 443 enslaved African Americans. Because the Americans believed they needed enslaved workers, Austin negotiated with the Mexican government to gain approval, as the new nation was opposed to slavery. Mexico abolished it in 1837.