Black Hawk's first county seat was at Cedar Falls, but the position was contested by Waterloo and a mob from Waterloo tried unsuccessfully to steal the county records in 1854. A referendum moved the county seat to Waterloo and the first courthouse was built in the 1850s in an inconvenient location on land belonging to the county judge. This was replaced in 1902 and a third courthouse was built in 1960. Waterloo is home to the Grout Museums, which include the Grout Museum of History and Science (1956), based around the collection of Waterloo financier Henry W Grout, the Rensselaer Russell House Museum (1861), Bluedorn Science Imaginarium, a hands-on science exhibition, and the Waterloo Museum of Art, which also facilitates theatre, symphony concerts, music, and dance. The Hawkeye Institute of Technology (1966) is in the city. The National Dairy Cattle Congress is held in Waterloo every September.

Waterloo was home to the five Sullivan brothers, all killed aboard the cruiser, USS Juneau, sunk by the Japanese in 1942. After this the US Congress passed the Sullivans Law which prevented brothers from serving on the same ship. Two US warships have subsequently been named USS The Sullivans. The Sullivans' story was the loose inspiration for the film Saving Private Ryan (1998).