Jefferson is a city in Marion County, Oregon, United States.

The city sits on the right bank of the Santiam River between Salem and Albany along Oregon Route 164 east of Interstate 5.

[5] Conser was also involved in the communities of Syracuse and Santiam City, which were about 2 miles (3 km) downstream of Jefferson.

[5] Jefferson post office was established in 1861, with a name change from Syracuse, and previously, Santiam City.

[5] In 1974, the Jacob Conser House was listed on the National Register of Historic Places (NRHP), which served as the city's library until 2018.

[6] The current Oregon Route 164 bridge across the Santiam was designed by Conde McCullough and named in Conser's honor.

[8] This region experiences warm (but not hot) and dry summers, with no average monthly temperatures above 71.6 °F (22.0 °C).

16.0% of all households were made up of individuals, and 6.7% had someone living alone who was 65 years of age or older.

16.4% of all households were made up of individuals, and 5.9% had someone living alone who was 65 years of age or older.