[1] However, some of the founders were never active student members because they had graduated before the June organizational meeting, including Beecher, Bateman, and Willard.

[1][2] The literary society was nameless until the fall of 1844, Henry M. Lewis suggested calling the group "Union and Progress"; Willard selected the name Sigma Pi and the corresponding Greek Words, Sustasis kai Prokape.

[6][7] By 1870, the society had a sizeable library of some 1,500 volumes, including biographies, Congressional records, dictionaries, dramas, encyclopedias, essays, history, magazines, novels, poetry, religion, science, theology, and travel.

[7] When Illinois College admitted women in 1903, the society invited female students to its meetings, turning this into a social event.

[4][8] Although it retains its identity as a literary society, it has become an unofficial social fraternity by the later 1990s, known for hosting parties in Beecher Hall.

[10] At the time, academic Becky Bradway-Hesse called it "the strongest, most active, and most elite society at Illinois College".

[1] Sigma Pi assembles three judged literary productions each semester where society members make a presentation to an audience.

[11] At the time, the fraternity expanding and Patterson wanted it to be the largest and oldest group of its kind in the nation; the literary society also provided a potential link to Patterson's hero William Jennings Bryan who was a member of the society.

[12][11] Patterson's history reported on a meeting with Bryan on February 8, 1908, to "exchange greetings and hope for the future prosperity of the fraternity".

[12] Baird wrote article stating that Sigma Pi fraternity's claim of "alleged antiquity" was "incredible" and "ridiculous".

[12] In the 1960s, Sigma Pi was open about its practice of hazing of new members, as documented in yearbook photos showing pledges covered in mustard and ketchup.

[13] The pledge master and president were criminally charged with hazing, had to resign from their offices, and were moved to inactive status.