After Boulder was selected as the site of the State University in 1872, Boulder citizens rallied to raise $15,000 in matching funds to construct CU's first building, now known as Old Main, on land donated by three prominent citizens. The result was a fine three-story red-brick building with two towers rising from the treeless plateau above Boulder Creek. Completed in 1876, it contained the living quarters for the president and his family, classrooms, library, laboratories, and rooms for the building custodian and his family.

Eight years later, smaller buildings were added nearby, housing men, women, and the university president. The construction of Woodbury Men's Residence Hall in 1890 and Hale Science in 1892 set the stage for an expanded formal campus. In the next 30 years, the university grew around a large cruciform-shaped open space that became Norlin Quadrangle, now listed in the State and National Registers of Historic Places. Significant buildings added during this time include Buckingham Library (now the University Theatre), Guggenheim Law (now Guggenheim Geography), Macky Auditorium, additions to Hale Science, and a Power House for steam generation.

The university's physical growth included more than the construction of buildings. Mary Sewall, wife of the university's first president, was responsible for much of the early landscaping. She beautified the barren surroundings with large green lawns and many trees. In these early years, students requested that sidewalks be laid from Boulder up the steep hill to campus to solve the problem of muddy footpaths. In 1888 faculty members and students started the tradition of planting trees on campus every Arbor Day, an annual tradition that continues to this day. In spite of these efforts, the campus lacked coherence in its architecture and landscaping, leading George Norlin, then a classics professor, to observe in 1916 that the campus looked like "a third rate farm."