"Mag" by Carl Sandburg was offered by Poets.org's Poem-A-Day on January 18, 2014. A link to the poem may be found here: http://www.poets.org/viewmedia.php/prmMID/23845. The editor of Poem-A-Day notes that "Mag" was first published in 1916 in Sandburg's collection, Chicago Poems, which helped establish the poet's reputation.
Carl Sandburg (1878 - 1967) (pictured) is perhaps most famous for his definitive biography of Abraham Lincoln for which he was awarded a Pulitzer Prize in 1940. He was awarded a second Pulitzer for his Complete Poems in 1951. Additional biographical information may be found here:
"Mag" is a sonnet. Sonnet's are known for being a vehicle for the expression of romantic love. Accordingly, the choice to use the sonnet form here is deliberately ironic.
Sandburg spent his late teens as a hobo in Kansas. The wish of the speaker to be "a bum on the bumpers" evokes this time in Sandburg's life, as does the general wish to be free of his ill-considered marriage and children.
It is not clear if Sandburg is the speaker in this poem. He married Lillian "Paula" Steichen in 1908, and, by all accounts, they were happy. They had two daughters, one of whom died shortly after she was born in 1913, the other born the year the poem was published, 1916. This poem does make one wonder if Sandburg was experiencing a little "seven year itch" when he composed "Mag" which was published about seven years after he married and the same year that he became saddled with the responsibilities of fatherhood.