The Greenwood District was one of the most prominent concentrations of African-American businesses in the United States during the early 20th century, it was popularly known as America's "Black Wall Street".
Greenwood Avenue in Tulsa was important because it ran north for over a mile from the Frisco Railroad yards, and it was one of the few streets that did not cross through both black and white neighborhoods. The citizens of Greenwood took pride in this fact because it was something they had all to themselves and did not have to share with the white community of Tulsa. Greenwood was home to a thriving Black commercial district, whose many red brick buildings belonged to Black Americans and housed thriving businesses, including grocery stores, banks, libraries, and much more; one of the most affluent African-American communities in the country, leading to the nickname, "Black Wall Street."
Source: PBS - The Rise and Fall of Jim Crow
Mann Brother's Grocery store was owned by J.D. Mann. This grocery store was located farther down on Lansing Street, next door to Gibbs' Fish and Poultry.