Here's a comprehensive summary of the Wikipedia article about Arena Stage:
Arena Stage, founded in Washington, D.C., in 1950 by Zelda and Thomas Fichandler and Edward Mangum, is a pioneering not-for-profit regional theater that helped launch the U.S. regional theater movement. It made history as the first racially integrated theater in D.C. and holds the distinction of being the first regional theater to transfer a production to Broadway with its original cast, famously with The Great White Hope in 1967 starring James Earl Jones.
Throughout its history, Arena Stage has achieved numerous "firsts," including presenting U.S. plays in the Soviet Union (1973), being the first American theater company invited to the Hong Kong Arts Festival (1980), and pioneering Audio Description for visually impaired audiences (1981). Now housed in the Mead Center for American Theater since its 2010 renovation, it operates three stages and is the largest company in the country dedicated to American plays and playwrights.
Under current Artistic Director Hana S. Sharif, Arena Stage commissions new works through its Power Plays initiative and serves an annual audience of over 300,000. The company has received extensive recognition, including a special Tony Award for theatrical excellence in 1976 and over 600 Helen Hayes Awards.