Marshall Bolds Champlain was born on December 22, 1824, in Stafford, Genesee County, New York. Not long afterward, his family moved to Cuba, Allegany County, where he attended the common schools. Later, he studied at the Middlebury Academy in Wyoming County and commenced his legal studies with James A. Guernsey, of Pittsford, Monroe County, and Hon. A. S. Diven, of Angelica. Following his admission to the bar in 1843 at the age of 18, he set up a law office in Cuba.
Marshall Champlain was appointed District Attorney of Allegany County in 1845, and served in that position with distinction for four years. He returned to his thriving private practice and, three years later, he was nominated to run for the New York State Senate. He lost in the general election but, the following year, he was elected to the 1853 session of the New York State Assembly. There, he chaired the committee to inquire into the conduct of State officers, and in the Court for the Trial of Impeachments, he was one of the managers in the proceedings against Canal Commissioner John C. Mather.
Champlain was elected a Delegate-at-Large to the Constitutional Convention of New York in April 1861, and he spoke on the rights of naturalized citizens, suffrage, national banks and personal liberty. In July 1862, Governor Morgan appointed Champlain a member of the War Committee of his Congressional District and, in 1864, he was a delegate to the Chicago Convention, supporting the nomination of General McClellan.
In 1867, he was elected New York Attorney General, and two years later was re-elected to that office. While in office, he was the prosecutor of phrenologist Edward H. Ruloff who was charged with murder. Ruloff's conviction was affirmed by the New York Court of Appeals and his public hanging was the last to be carried out in New York State.
At the end of his second term as Attorney General, Marshall B. Champlain retired from public and professional life. He died suddenly at his home in Cuba, Allegany County on March 8, 1879 from an attack of pneumonia.
Life Sketches of Executive Officers and Members of the Legislature, Volume 3 (1870)
A Democratic Politician Gone. New York Times, March 9, 1987.