South Texas is a region of the U.S. state of Texas that lies roughly south of—and includes—San Antonio. The southern and western boundary is the Rio Grande, and to the east it is the Gulf of Mexico. The population of this region is about 4.96 million according to the 2017 census estimates. The southern portion of this region is often referred to as the Rio Grande Valley. The eastern portion along the Gulf of Mexico is also referred to as the Coastal Bend. Greater Houston and Beaumont–Port Arthur are occasionally tied to the region, both for physically being on the southern end of the state and for businesses that use "South Texas" in its name. (i.e. South Texas School of Law, South Texas State Fair, etc). However, the two are more commonly associated with East Texas or Southeast Texas. Geography There is no defined northern boundary, although it is believed to be at the city of San Antonio and from an east to west line extending from the Rio Grande near Maverick County to the Gulf of Mexico, but turning southeast at or near Lavaca County, and continuing towards the Gulf of Mexico to separate it from East Texas and Southeast Texas. The Rio Grande serves as the western and southern boundaries and separates Texas from Mexico. The eastern portion of South Texas is bordered by the Gulf of Mexico. South Texas consists of 41 counties. Its terrain is flat, lying on the coastal plain. South Texas is so vast, that there are even subregions. The very southern tip of South Texas, called the Rio Grande Valley, has fertile soils and is known for its citrus production. The eastern portion of South Texas is often referred to as the Coastal Bend; here, coastal salt marshes, estuaries, and wetlands are scattered all around. The western and central parts are known as the South Texas Plains or the Brush Country. Mesquite trees and crop fields dominate the Brush Country. Counties The fastest growing county in South Texas is Guadalupe County, growing by 31.3% from 2010 to 2020. The slowest growing county in South Texas is Refugio County, shrinking by 8.7% from 2010 to 2020. Cities Some people consider Houston to be in South Texas for several reasons: numerous businesses in the Houston region contain 'South Texas' in their titles. The United States District Court for the Southern District of Texas includes the