Maverick County is in the northwestern section of the Rio Grande plain region in southwest Texas. The Rio Grande forms Maverick County's western and international border with Mexico; the county is bordered on the north by Kinney County, on the east by Zavala County, and on the south by Webb County. Eagle Pass, the county seat and most populous community, is in southwestern Maverick County on the Southern Pacific Railroad, immediately east of the Rio Grande opposite Piedras Negras, Mexico.