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.
The first name for this locality was Conser's Ferry, for Jacob S. Conser, an Oregon Trail pioneer of 1848 who ran a ferry across the Santiam River. Conser was also involved in the communities of Syracuse and Santiam City, which was about 2 miles (3 km) downstream of Jefferson. He established the ferry in 1851, and also served as the postmaster of Santiam City. When the Jefferson Institute was established in the vicinity (not the same as the Jefferson Institute in Polk County), the name Jefferson was eventually adopted by the community. Jefferson post office was established in 1861, with a name change from Syracuse, and previously, Santiam City.
In 1974, the Jacob Conser House was listed on the National Register of Historic Places (NRHP), which serves as the city's library. The current Oregon Route 164 bridge across the Santiam was designed by Conde McCullough and named in Conser's honor.