Authorities say the robber hit banks in Fawn Grove, Pa., on July 19; West Lampeter, Pa., on July 27, and Wilmington, Del. on Aug. 12.
In each robbery, the man entered the bank and displayed a handgun. He confronted a teller and demanded cash. After getting an undisclosed amount of money, the man then fled on foot.
No one was injured during the robberies.
The robber is described as a white male, 55 to 60 years old, 6 feet tall, with gray hair and a goatee.
Citizens can contact the Delaware State police at 302-834-2630 ext. 254 or the Pennsylvania State police at 717-428-1011.