Tuscaloosa is a city in and the seat of Tuscaloosa County in west-central Alabama, United States, on the Black Warrior River where the Gulf Coastal and Piedmont plains meet. Alabama's fifth-most populous city, it had an estimated population of 110,602 in 2023. It was known as Tuskaloosa until the early 20th century. It is also known as "the Druid City" because of the numerous water oaks planted in its downtown streets since the 1840s.