WASHINGTON — Stephen A. Schwarzman, the 57-year-old president and co-founder of investment firm the Blackstone Group, has been named chairman of the John F. Kennedy Center. He succeeds James A. Johnson, who ankled in January after eight years in the post.

Schwarzman’s unanimous selection by the center’s board of trustees ends a search that began last April after Johnson, a former chairman of Fannie Mae, revealed his intentions to depart. The high-profile exec sets the center’s direction and leads its considerable fund-raising activities.

Schwarzman assumes the helm of an organization that is on solid footing both financially and artistically. Under the leadership of president Michael M. Kaiser, who handles day-to-day operations and the org’s artistic direction, the Kennedy Center is enjoying success on all fronts. It’s basking in the national limelight of “Tennessee Williams Explored,” a four-month celebration of the playwright, and has embarked on a $250 million capital expansion project.

“Steve’s impressive qualifications in the business world, combined with his commitment to the arts and education, make him ideal for this next stage of the center’s growth,” said Alma Powell, wife of Secretary of State Colin Powell, who has served as interim co-chairman along with Kenneth Duberstein.

Before helping form the Gotham-based Blackstone Group in 1985, Schwarzman was managing director of Lehman Brothers. He is on the board of directors of the New York City Ballet, the Film Society of Lincoln Center, the New York Public Library and New York City Partnership. He becomes the center’s fifth chairman. Others include its founding chairman Roger L. Stevens, Ralph P. Davidson and James D. Wolfensohn.