Police received a 911 call from the clerk at the USA Gas Station at 199 S. Orchard Ave. at 11:24 p.m., police said.
The female clerk told police that the station had just been robbed and that the suspect had fled on foot.
Police discovered that the suspect had forced his way into the business shortly after it closed and ordered the clerk to the ground.
The suspect made off with an undisclosed amount of cash from the register and fled the scene on foot.
He is described as black man of unknown age, standing about 6 feet 2 inches tall and weighing about 230 pounds, police said.
The suspect had long black hair and was last seen wearing a black hooded sweatshirt pulled up tight over his head.
He was last seen running east toward East Monte Vista Avenue, according to police.
No weapon was seen during the robbery.
Anyone with information about this incident is asked to contact Detective Todd Dye at (707) 449-5212.