The Library of Congress is to announce Thursday that the next poet laureate is Natasha Trethewey, the Pulitzer Prize-winning author of three collections and a professor of creative writing at Emory University in Atlanta. Trethewey, 46, was born in Gulfport, Miss., and is the first Black U.S. poet laureate since Rita Dove in 1993.

“I’m still a little in disbelief,” Trethewey said on Monday.

Unlike the recent laureates, Trethewey, who will officially take up her duties in September, is still in midcareer and not well-known outside poetry circles. Her work combines free verse with more traditional forms like the sonnet and the villanelle to explore memory and the racial legacy of America. Her fourth collection, “Thrall,” is scheduled to appear in the fall. She is also the author of a 2010 nonfiction book, “Beyond Katrina: A Meditation on the Mississippi Gulf Coast.”