[7] The city was named after Lucius Quintus Cincinnatus Lamar, a Confederate soldier and diplomat who wrote the Mississippi Secession Ordinance, and after the Civil War, went on to serve as U.S. Secretary of the Interior and U.S. Supreme Court Justice.

[10] It was named after Lucius Quintus Cincinnatus Lamar II, U.S. Secretary of the Interior, the author of the Mississippi Ordinance of Secession, and a Confederate officer and diplomat.

The northern site of the Pierre Auger Observatory of ultra-high energy cosmic rays is planned to be built near Lamar.

[11] The city lies in southeastern Colorado in northwestern Prowers County on the south side of the Arkansas River floodplain.

Lamar is one of the rare American places with an antipode located on land and not in the open sea.

According to the United States Census Bureau, the city has a total area of 4.2 square miles (11 km2), all land.

Males working full-time and year-round had a median income of $31,621 versus $30,148 for females.

The hospital has an emergency department that is a level IV trauma center.