Promotus Advertising, (from Latin Promotus, meaning: "to advance (someone) to a higher grade or office"; "to move forward, advance"; "to further the growth or progress of (anything).") located in Indianapolis, Indiana, was started in 1983 by Bruce Bryant during a time when there were very few African Americans working in the advertising business and no African American owned agencies.
Promotus Advertising was started in the 20th century.
It's definitely correct because it was started in 1983, which is in the 20th century. It's difficult because the system doesn't seem to understand what is encapsulated in a century and what that means exactly.