As Detroit's manufacturing base boomed during two world wars (1917 ~ 18 and 1942 ~ 45), large numbers of African Americans moved here to work in the factories. Detroit's African American population increased from five thousand in 1910 to three hundred thousand by 1950. Throughout this period segregationist policies restricted were blacks could live, own businesses, and spend their free time. During the 1930s a commercial center emerged in the area roughly bounded by Adams, Brush, Alexandrine and Hasting Street (replaced by I-75). Known as 'Paradise Valley,' it had black-owned medical offices and retail shops as well as swank restaurants and hotels. Some night-clubs, called 'black and tans' were frequented by blacks and whites alike. African Americans owned and operated all of the businesses in the valley.