Lamar is a city located in the U.S. state of Arkansas. It is within Johnson County. It has a total area of 4.64 square miles at 35°26′26″N 93°23′34″W. The elevation is 440 feet above sea level. As of the 2010 census data, it had a total population of 1,605. The population density was 361.86/sq mi. Estimated per capita income in 2015 was $18,734. It is using Zip code 72846.