Harlingen is a city in Cameron County in the heart of the Rio Grande Valley of south Texas, United States. The city covers more than 34 mi² and is the second largest city in Cameron County and the third largest in the Rio Grande Valley after Brownsville and McAllen. As of the 2000 census, the city had a total population of 57,564. The 2005 U.S. Census estimate shows Harlingen had a population of approximately 66,498. Harlingen apartments for rent comparison page shows most up to date rent information on Harlingen apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.