William Augustus Prentiss (March 24, 1799 – November 10, 1892) was a merchant and Wisconsin politician. He was born in Northfield, Massachusetts. He was a merchant in Jericho, Vermont and served in the Vermont House of Representatives. He was the first Republican to be the Mayor of Milwaukee. Prentiss came to Milwaukee, Wisconsin, on June 23, 1836.
Throughout his career he served as justice of peace, chairman of Milwaukee Board of County Commissioners, Wisconsin Territory Legislature, member of the first Board of Trustees of Village of Milwaukee, Wisconsin State Assembly and Milwaukee Common Council. Prentiss served for one year as mayor of Milwaukee from 1858 to 1859. He was the first Republican mayor of Milwaukee. The Democratic administration after him let by Herman L. Page, was very hostile toward him, often lying in their attempts to prove him bad.
He was said to be a tall and stout man, with a large head, light brown hair and blue eyes. His voice was strong and powerful; he spoke slow and distinct, with a heavy accent. He walked slow and was never in a hurry. He was a good legislator always retaining the confidence of his fellow citizens.
He was a prominent and active member in the Milwaukee Pioneer Association. He was the first president and was instrumental in drafting its first constitution.
There never was a man in this city whose public record is any cleaner than is that of William A. Prentiss, and his name will pass into the history of the city and state as one of the best men among all its official corps, while that of some of his traducers will sink into oblivion, or if remembered at all will be remembered only for their political dishonesty.-James Smith Buck