WISR is a commercial AM radio station licensed to Butler, Pennsylvania. The station was the first to go on the air in Butler County, doing so on September 26, 1941. The station was the very last to be granted a broadcast license before the FCC halted the licensing of any additional stations until after World War II. It has always broadcast on AM 680 with a maximum power output of 250 Watts, non-directional. The station had operated as a daytime-only station until it was granted limited nighttime power in the late 1980s.