<Tr> <Td_colspan="2"> Map of the Rio Grande Valley </Td> </Tr> <Tr> <Td_colspan="2"> Website: Handbook of Texas: Rio Grande Valley </Td> </Tr> <P> The Rio Grande Valley is an area located in the southernmost tip of South Texas . It lies along the northern bank of the Rio Grande river, which separates Mexico from the United States . The four - county region, consisting of Hidalgo, Cameron, Willacy, and Starr counties, is one of the fastest growing places in the United States . From having about 325,000 people in 1969, to today a population over 1,300,000 in 2014 . Some of the biggest cities in the region are: Brownsville, Harlingen, Weslaco, Pharr, McAllen, Edinburg, Mission, Hidalgo, and Rio Grande City . </P> <P> The Rio Grande Valley is not a true valley, but a floodplain, containing many oxbow lakes or resacas formed from pinched - off meanders in earlier courses of the Rio Grande . Early 20th - century land developers, attempting to capitalize on unclaimed land, utilized the name "Magic Valley" to attract settlers and appeal to investors . The Rio Grande Valley is also called El Valle, the Spanish translation of "the valley", by those who live there . The residents of the Rio Grande Valley no longer refer to the area as "El Mágico Valle del Río Grande" ("The Magical Valley of the Rio Grande"), but as "The Valley" and also simply by the initials R.G.V. </P>

How many counties make up the rio grande valley