Natasha Trethewey at the Library of Congress, Jan. 30, 2013. Natasha Trethewey at the Library of Congress, Jan. 30, 2013.

One hundred and fifty years later, Americans are still fighting the Civil War, US Poet Laureate Natasha Trethewey said at the Library of Congress on Wednesday. The field of battle is now historical memory, and gatling guns have been replaced by symbols, but the contest over what sort of nation this will be — and was — continues, according to the 46-year-old poet.

Before a standing-room-only crowd of 300 people, Trethewey focused her remarks on Walt Whitman’s complicated response to black soldiers. Her lecture — in association with the Library’s “Civil War in America exhibit — elegantly blended scholarship, cultural criticism and poetry.

The war poems in Whitman’s “Leaves of Grass” are justly hailed as “monuments to the common solider,” Trethewey said, but she noted that his verse also reflects the racial attitudes of his time. “Whitman leaves out the reality of the faces of so many soldiers who were not white,” she said, “even as his inclusive language reminds us of the freed men all over the South.”

While acknowledging his radical liberalism, Trethewey insisted that Whitman perpetuated the national mythology that “blacks were passive recipients of freedom” given to them by brave white soldiers. In fact, many blacks fought and sacrificed their lives in the Civil War.

When she toured historic sites in her native Mississippi, where “the dead stand up in stone,” she found the same act of erasure still being carried out by memorials, plaques and even tour guides working for the Park Service. The record is “rife with omission and embellishment” that keeps “blacks relegated to the margins of historical memory,” she said. The Daughters of the Confederacy worked diligently to make sure that Americans remember the Civil War “only in terms of states’ rights, not in terms of slavery.”

Trethewey’s lecture this week was a kind of homecoming. Ten years ago, she conducted research on black soldiers in the Library of Congress and composed parts of her Pulitzer Prize-winning collection, “Native Guard,” in the Main Reading Room. Her most recent collection, “Thrall,” explores her life as the daughter of an African American woman and a white man, the poet Eric Trethewey.

Trethewey is one of the youngest people ever to serve as US poet laureate. Asked by a member of the audience to list the three things she hopes to accomplish during her tenure, she said, “Bring poetry to a wider audience, bring poetry to a wider audience, bring poetry to a wider audience.”

Ron Charles is The Post’s fiction editor. You can follow him on Twitter @RonCharles.