Prosser was born on September 2, 1809, in the area which was separated as the Town of Westerlo, Albany County, New York in 1815.
[2] At an early age he removed to Albany, New York, and served as a clerk in the forwarding house of Dows & Cary there.
[2] Prosser entered politics as a Democrat, but his "Anti-slavery proclivities led him into the support of Mr. Van Buren for the Presidency" and he joined the Free Soil Party in 1848, and the Republican Party upon its foundation in 1855.
[5] Senator Prosser is rather prepossessing in his personal appearance, being about medium in height, with an active frame, sharp, grey eyes, and a bushy, iron-grey beard; and wears a cheerful good-natured, though dignified and somewhat reserved expression upon his countenance which, at once, gives assurance of the real man.
In 1880, Kate committed suicide by jumping from the roof of a five-story tenement at 430 East 14th Street in New York City.