Evanston police say the Wells Fargo Bank in the 2200 block of Howard Street was robbed around 10:30 this morning.
Police say the robber didn't display a weapon but implied he had one and then fled from the scene on foot.
Police say the robber is described as a black or Hispanic male in his 20s, 5-feet-4 to 5-feet-7-inches tall, with a slim build.
He was wearing a black Nike cap and a blue shirt over a red shirt.
No one was injured in the incident. Police say the bank will be closed until about 1 p.m. but other businesses in the area remain open as police continue their investigation.
Update 4:55 p.m.: Police Cmdr. Ryan Glew says the robber presented a note to two tellers at the bank announcing the robbery and claiming the he was armed.
The tellers gave the man an unspecified amount of cash and the robber fled the bank. He was last seen heading westbound toward McCormick Boulevard.
The Evanston Police Detective Bureau and the FBI are investigating the robbery. Anyone with information is encouraged to contact the Detective Bureau at 847-866-5040 or Text-A-Tip to CRIMES (274637) and then start your message with EPDTIP.