The earliest settlers to the area were the Ozark Bluff Dwellers. In 1836, the Creek Indians arrived via the Trail of Tears. It wasn't until the discovery of oil in the early 1900's, however, that Tulsa really began to develop. By the 1920's, Tulsa was a boomtown, dubbed by many as the Oil Capital of the World."" Today, business is still booming, thanks to a leading aerospace industry and a number of major corporations, including American Airlines. Tulsa also has its share of cultural attractions. Architecture buffs should check out the Art Deco façades at the Boston Building, Union Depot, and the Philtower. Art lovers can visit two fine museums—the Philbrook and the Gilcrease, the latter of which contains a copy of the Declaration of Independence. For something different, enjoy the beautiful grounds of Oral Roberts University."