Montgomery County is a county in the U.S. state of Texas. As of the 2020 U.S. census, the county had a population of 620,443. 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. Between 2010 and 2020, its population grew by 36%. According to the U.S. Census Bureau, the estimated population is 711,354 as of July 1, 2023.