Tulsa is the second largest city in the state of Oklahoma and 47th-largest city in the United States. Tulsa was first settled in the 1830s by the Lachapoka Band of Creek Native American tribe. In 1921, it was the site of the infamous Tulsa Race Riot, one of the largest and most destructive acts of racial violence in the history of the United States. For most of the 20th century, the city held the nickname "Oil Capital of the World" and played a major role as one of the most important hubs for the American oil industry. Once heavily dependent on the oil industry, economic downturn and subsequent diversification efforts created an economic base in the energy, finance, aviation, telecommunications and technology sectors.