Waterloo is a city in Linn County, Oregon, United States.

The city's name, a joking reference to the Battle of Waterloo, stemmed from a 19th-century court decision that settled a land dispute at Kees Mill along the South Santiam River.

[6] The federal government established a post office at Waterloo on January 5, 1875.

[5] According to the United States Census Bureau, the town has a total area of 0.12 square miles (0.31 km2), all land.

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

20.5% of all households were made up of individuals, and 9.6% had someone living alone who was 65 years of age or older.

About 10.9% of families and 11.7% of the population were below the poverty line, including 8.8% of those under the age of eighteen and 13.8% of those 65 or over.