The son of an attorney from John L. Hamilton was born in Bloomington, Illinois. His family moved to Chicago and Hamilton graduated from the Chicago Manual Training School, where he likely first learned architectural drafting. In 1897, Hamilton became a draftsman for the Chicago Board of Education earning a salary of $15 per week and working under the supervision of head architect Normand Patton.
Hamilton joined the Chicago Architectural Club in 1903. Known originally as the Chicago Architectural Sketch Club, the organization provided draftsmen with a forum to improve skills and show their talents at a time when many aspiring young architects had no access to formal training. An active member of the club, Hamilton became first vice president soon after joining. In 1904, he headed the exhibition committee and was appointed as the club’s president.
By 1903, Hamilton had begun accepting architectural commissions, to design buildings such as a stores, offices, and apartments. At the same time, he continued working at the Board of Education, now earning $35 per week. (He left this position around 1905.)
In 1905, Hamilton formed a partnership with Prairie School architect Dwight Heald Perkins. That same year, Perkins became the Board of Education’s head architect. Hamilton ran the busy private office while Perkins also continued in his position with the Board of Education until 1910. The following year, Perkins and Hamilton added a third partner, William K. Fellows. Also active in Chicago Architectural Club, Fellows had previously been a partner in the firm of Nimmons and Fellows, which was known for designing in the Prairie style. Perkins, Fellows and Hamilton designed many significant buildings, including the Lion House in Lincoln Park Zoo and the Daily New Fresh Air Sanitarium in Lincoln Park. The firm remained in business until 1927.