Gladewater is a city in Gregg and Upshur counties in the U.S. state of Texas with a 2020 census population of 6,134. In the early 20th cent…Gladewater is a city in Gregg and Upshur counties in the U.S. state of Texas with a 2020 census population of 6,134. In the early 20th century, Gladewater was an oil boom town. In 1995, the Texas Legislature proclaimed it the "Antique Capital of East Texas."