Fort Bend County is a county in the U.S. state of Texas. As of the 2010 census, its population was 585,375, making it the tenth-most populous county in Texas. The county seat is Richmond, while its largest city is Sugar Land. The county was founded in 1837 and organized the next year. It is named for a blockhouse at a bend of the Brazos River; the fort was the start of the community in early days.