There are actually two distinguished Americans with the name Oliver Wendell Holmes, the poet and physician Oliver Wendell Holmes Sr. and his son the jurist Oliver Wendell Holmes Jr.
Oliver Wendell Holmes, Sr. (August 29, 1809 – October 7, 1894) was a well respected poet and doctor. He was born into a wealthy family and attended Phillips Academy and Harvard. He received his MD from Harvard in 1836. Some of his best know works include the poem "Old Ironsides", published in 1830, and the essay collection The Autocrat of the Breakfast-Table (1858). As a doctor, he was one of the earliest to suggest that puerperal fever was contagious and could be prevented by strict hygienic practices. He also coined the word "anesthesia".
Oliver Wendell Holmes, Jr. (March 8, 1841 – March 6, 1935) was a lawyer who served on the Supreme Court from 1902 to 1932. He served in the Twentieth Regiment of Massachusetts Volunteer Infantry in the Civil War and afterwards obtained a law degree from Harvard. He advocated a position known as legal realism and was one of most influential legal thinkers in US history.