The Michigan Union was formed in 1904 as an "all inclusive organization" focused on providing feelings of unity for men on campus. The first meeting was held in Waterman Gymnasium and was attended by over 1100 students. From the beginning, the Michigan Union founders were adamant about finding a "home" for the organization, and in 1907 they purchased the former house of Judge Thomas M. Cooley on State Street. The building, however, proved inadequate for their needs, and in 1910 the members sought to construct a more suitable building. Brothers and University alumni Allen B. and Irving K. Pond were hired as architects. In 1916 the Thomas Cooley house was demolished and construction of the Michigan Union began. Funds for completion of the interior of the building were secured in pledges, but due to the war in the spring of 1917, the money proved difficult to collect. While in its unfinished state the building was used as a barracks and mess hall by the Student Army Training Corps. After the war ended, the Union's interior was completed. The Michigan Union officially opened in 1919.
The original Union contained a bowling alley in the basement and a barbershop and student eatery on the ground floor. It also included lounges, reading rooms, committee rooms, dining rooms, a billiard and games room, an assembly room, and accommodations for returning alumni. The swimming pool, which was included in the original design but remained unfinished due to lack of funds, opened in 1925. The Michigan Union initially operated as a club, with all members paying yearly dues of $2.50. By 1914 there were over 4,000 members, which was a considerable portion of the University student body and indicative of the strength of the organization. In 1918 the Regents authorized that the membership fee, then $3.00, be collected from all students. In 1918 the fee was increased to $5.00, and all male students automatically became Union Members. The Michigan Union operated through a Board of Directors composed of students, faculty and alumni. This board allowed for expression of student concerns, and many students voluntarily devoted their time to Union activities.
Initially, women were only allowed to enter the Michigan Union through the North entrance and when accompanied by a male escort. It was the founders' belief that women already had a social center in the parlors of the Barbour Gymnasium. In 1929, the Michigan League was constructed and opened on North University Avenue. The League, also designed by the Pond brothers, was created as a center for women's social, cultural and recreational campus activities. In 1954, for the first time in its history, women were allowed to enter the Michigan Union without an escort, even through the front doors. The Billiards room, however, held to the old traditions and it was not until 1968 that women were granted equal access to the entire building.
The building has witnessed many changes over the years, including the closing of the swimming pool, the creation of more vendor space and student offices, and the addition of the International Student Center. The fourth floor, which originally consisted of hotel rooms for returning alumni, was turned into student offices in 1972 and completely renovated in 1994. Today the Michigan Union hosts a broad array of services, programs, and facilities focused on serving the students and other members of the University and community.