Please answer a question about the following article about University of Kansas:

The site selected for the university was a hill known as Mount Oread, which was owned by former Kansas Governor Charles L. Robinson. Robinson and his wife Sara bestowed the 40-acre (16 ha) site to the State of Kansas in exchange for land elsewhere. The philanthropist Amos Adams Lawrence donated $10,000 of the necessary endowment fund, and the citizens of Lawrence raised the remaining cash by issuing notes backed by Governor Carney. On November 2, 1863, Governor Carney announced that Lawrence had met the conditions to get the state university, and the following year the university was officially organized. The school's Board of Regents held its first meeting in March 1865, which is the event that KU dates its founding from. Work on the first college building began later that year. The university opened for classes on September 12, 1866, and the first class graduated in 1873.

What was the year in which KU's first roster of students graduated?
1873