According to the United States Census Bureau, the city has a total area of 10.73 square miles (27.79 km²), of which 10.13 square miles (26.24 km²) is land and 0.60 square miles (1.55 km²) is water.

Onalaska lies immediately north of La Crosse, on the Black River.
It is the second largest city in La Crosse County.

Named streams within the current corporate limits of the city include the Black River, the La Crosse River and Sand Lake Coulee Creek.
In the 1930s, the construction of Lake Onalaska resulted in the flooding and eventual disappearance of a shallow, natural body of water, Rice Lake, and several smaller ponds in the Black River bottoms area.

Brice Prairie is an urban reserve area within the City of Onalaska, located below the ridge on which most of the city is situated.
It lies to the northwest of the city's current northern border, and is directly on Lake Onalaska.
According to the United States Census Bureau, the city has a total area of 10.73 square miles (27.79 km²), of which 10.13 square miles (26.24 km²) is land and 0.60 square miles (1.55 km²) is water.
Onalaska lies immediately north of La Crosse, on the Black River. It is the second largest city in La Crosse County.
Named streams within the current corporate limits of the city include the Black River, the La Crosse River and Sand Lake Coulee Creek. In the 1930s, the construction of Lake Onalaska resulted in the flooding and eventual disappearance of a shallow, natural body of water, Rice Lake, and several smaller ponds in the Black River bottoms area.
Brice Prairie is an urban reserve area within the City of Onalaska, located below the ridge on which most of the city is situated. It lies to the northwest of the city's current northern border, and is directly on Lake Onalaska.
Onalaska, Wisconsin