Jefferson is a city in Marion County, Oregon, United States. It is part of the Salem Metropolitan Statistical Area. The population was 3,098 at the 2010 census. It is home to the annual Mint Harvest Festival and is the self-proclaimed "Mint Capital of the World" as well as "Frog Jumping Capital of Oregon." The city sits on the right bank of the Santiam River between Salem and Albany along Oregon Route 164 east of Interstate 5.