Sequel to Drum-Taps, subtitled When Lilacs Last in the Dooryard Bloom'd and other poems, is a collection of eighteen poems written and published by nineteenth-century American poet Walt Whitman in 1865. Most of the poems in the collection reflect on the American Civil War (1861–1865), and the collection includes two elegiac poems, When Lilacs Last in the Dooryard Bloom'd and O Captain! My Captain!, written in response to the Assassination of Abraham Lincoln in 1865. These poems were later included in Leaves of Grass, Whitman's comprehensive collection of his poetry that was expanded throughout his life.
At the start of the American Civil War (1861–1865), Whitman moved from New York City to Washington, D.C. where he obtained work in a series of government offices, at first with the Army Paymaster's Office and later with the Bureau of Indian Affairs. He volunteered as a nurse in the army hospitals. His experience as a nurse informed his poetry which matured into reflections on death and youth, the brutality of war, patriotism, and offered stark images and vignettes of the war. Many of his Civil War poems were assembled into a collection that Whitman titled Drum-Taps.
After the publication and printing of Drum-Taps in Brooklyn in April 1865, Whitman intended to supplement the collection with several additional Civil War poems and a handful of new poems mourning the assassination of President Abraham Lincoln that he had written between April and June 1865. After returning to Washington, D.C., in Summer 1865, Whitman contracted with Gibson Brothers to publish a pamphlet of eighteen poems that would include two works directly addressing the assassination—the elegy When Lilacs Last in the Dooryard Bloom'd and "O Captain! My Captain!". He intended to include the pamphlet with copies of Drum-Taps. The 24-page collection was titled Sequel to Drum-Taps and bore the subtitle When Lilacs Last in the Door-Yard Bloom'd and other poems. The title poem, When Lilacs Last in the Dooryard Bloom'd, filled the first nine pages. In October, after the pamphlet was printed, Whitman travelled to Brooklyn to collate and bind them into copies of Drum-Taps. Whitman added the poems from Drum-Taps and Sequel to Drum-Taps as a supplement to the fourth edition of Leaves of Grass printed in 1867 by William E. Chapin.