Lamar is a small, unincorporated community and census-designated place (CDP) in Aransas County, Texas, United States, 10 miles (16 km) north of Rockport and 40 miles (64 km) north of Corpus Christi. As of the 2010 census it had a population of 636. The community was named for Mirabeau B. Lamar, the second president of the Republic of Texas.Lamar was founded in 1839 at Lookout Point, on the channel entrance to Copano Bay.