The man was discovered on the southbound tracks in the 2500 block of South Archer Avenue about 4 a.m., Chicago police said. He was pronounced dead at the scene, police said.
Video footage shows the man attempting to climb a chain-link fence in an apparent effort to enter CTA property, according to a statement from transit agency. He fell from the fence and landed on the electrified third rail.
Area 1 detectives and the CTA were investigating.