Lee S. Tillotson was born on December 8, 1874 in Bakersfield, Vermont. Tillotson attended local schools, and graduated from Brigham Academy in 1890. He then joined the Central Vermont Railway in St. Albans, working as a clerk in its main office from 1890 to 1899.
Tillotson joined the Vermont National Guard in 1898. Enlisting as a cornet player, he rose in rank to become the principal musician of the 1st Vermont Volunteer Infantry Regiment during the Spanish–American War. He continued his military service after the war, obtaining a commission as a first lieutenant in 1901 and rising to the rank of lieutenant colonel. He was also an active member of United Spanish War Veterans.
During his life Tillotson continued to pursue his musical interests. He sang in and directed choirs in St. Albans, Boston and Washington, D.C., and also served as Treasurer of the Handel and Haydn Society.
Following the Spanish–American War Tillotson resigned from the Central Vermont Railroad to pursue legal studies in the office of St. Albans Attorney Alfred A. Hall. He attained admission to the bar in 1902 and began a practice in St. Albans.
A Republican, Tillotson served as Judge of the St. Albans Municipal Court from 1904 to 1906. Tillotson was also involved in other business and government activities, including serving as a member of the board of directors for the gas lighting company in St. Albans and a member of the Vermont Commission on Probation.