Waterloo is a city in Jefferson County in the U.S. state of Wisconsin, located between the cities of Madison and Milwaukee. The city is located within the Town of Waterloo. The population was 3,259 at the 2000 census.
Waterloo is located at 43°11′1″N 88°59′23″W / 43.18361°N 88.98972°W / 43.18361; -88.98972, (43.18366, -88.989965) at the intersection of Wisconsin Highway 89 and Wisconsin Highway 19.
According to the United States Census Bureau, the city has a total area of 3.9 square miles (10.2 km²), of which, 3.9 square miles (10.1 km²) of it is land and 0.04 square miles (0.1 km²) of it (0.51%) is water.