Short answers, pulled from the story.
Walt Whitman wrote O Captain! My Captain following the assassination of Abraham Lincoln on the 15th of April 1865. The poem first appeared in The Saturday Press newspaper on the 4th of November 1865.
O Captain! My Captain uses an AABBCDED rhyme scheme designed specifically for recitation. It consists of nine quatrains organized into three stanzas with a tetrameter trimeter ballad beat.
Initial reception to O Captain! My Captain was very positive following its November 1865 publication. A Boston Commonwealth reviewer called it the most moving dirge for Lincoln ever written in early 1866.
The poem transforms assassination into sort of martyrdom without specifically mentioning Lincoln by name. This approach allows general audiences to connect with themes of sacrifice and national grief through familiar religious symbols.
Poetry anthologies began including works considered more authentic to his style shortly after World War II ended. Michael C. Cohen observed the poem all but disappeared from American anthologies after 1966.