While at Harvard College, Dana had an attack of the measles which affected his vision. Thinking it might help his sight, Dana, rather than going on a Grand Tour as most of his fellow classmates traditionally did (and unable to afford it anyway) and being something of a non-conformist, left Harvard to enlist as a common sailor on a voyage around Cape Horn on the brig Pilgrim. He returned to Massachusetts two years later aboard the Alert (which left California sooner than the Pilgrim).
He kept a diary throughout the voyage, and, after returning, he wrote a recognized American classic, Two Years Before the Mast, published in 1840, the same year of his admission to the bar.