Hoar was born in Worcester, Massachusetts, and graduated from Harvard University in 1876.

He was a member of Company C, Fifth Massachusetts Infantry, from 1875 to 1879, an assistant to the district attorney for the middle district Worcester County, Massachusetts from 1884 to 1887, a member of the common council of Worcester from 1887 to 1891, and aide-de-camp with the rank of colonel on the staff of Governor Oliver Ames from 1887 to 1890.

[1] Hoar died in Worcester after an illness of about five weeks and is buried in the Rural Cemetery there.

Since his death occurred five days before the next election, the Third Congressional Republican District Committee, which was in session at the time of his death, nominated Charles G. Washburn to fill the vacancy, and he won the seat.

Congressman Samuel Hoar and the great grandson of Roger Sherman.