Montgomery County is a county in the U.S. state of Texas. As of the 2010 census, its population was 455,746. A 2019 estimate places the population at 607,391. The county seat is Conroe. The county was created by an act of the Congress of the Republic of Texas on December 14, 1837 and is named for the town of Montgomery. Between 2000 and 2010, its population grew by 55%, the 24th-fastest rate of growth of any county in the United States.