County Seat History
Hempstead Grew Because of the Railroad, Not the River
Hempstead became the county seat of Waller County because the Houston and Texas Central Railway chose it as a terminus in 1858, making it a major trade hub almost overnight.
Before the railroad, most settlers were along the Brazos River bottoms. When the Houston and Texas Central Railway reached northwest of Houston in 1858, Hempstead formed at that spot and was incorporated in November of the same year. It quickly became a trading center for the surrounding cotton plantation economy.
Waller County itself was not created until 1873, carved from parts of Austin and Grimes counties. It was named for Edwin Waller, a signer of the Texas Declaration of Independence. Hempstead has served as county seat since the county's founding. Today it is home to about 6,000 people and sits roughly 50 miles northwest of Houston on US Highway 290.
Source to confirm: Handbook of Texas — Waller County