Patterson had wanted to join the Sigma Pi literary society at Illinois College in Jacksonville, Illinois, but after his request to expand the society to OSU was declined, he approached Tau Phi Delta members, claiming to represent a historic fraternity called Sigma Pi that dated to the 18th century.

Tau Phi Delta accepted Patterson's invitation to merge and adopted the name Sigma Pi.

[3] Sigma Pi oversees several charitable programs, including the Altruistic Campus Experience[4] (ACE), and maintains the Sigma Pi Educational Foundation "to assist needy and deserving students to complete their education, and to aid aged or disabled former students who are in need or worthy of assistance."

On January 26, 1897, Charlotte N. Mallote, a professor of Latin and French, spoke to a group of students during chapel hour at Vincennes University about College Fraternities.

By the end of its first year in 1898, Tau Phi Delta had 10 members, but the new Fraternity encountered membership struggles at the turn of the 20th century, with many of America's young men leaving to fight in the Spanish–American War.

Personal endeavors were paused, while national efforts and resources focused on the war in the Caribbean and Pacific Oceans.

Failing at these, Patterson fabricated a history of Sigma Pi, claiming it was founded in 1752 at the College of William & Mary with members such as James Madison, Thomas Jefferson, and Robert E. Lee.

He then contacted Tau Phi Delta, which accepted his fabricated history and consolidated under the Sigma Pi name.

Bryan, a member of Delta Chi and the unrelated Sigma Pi literary society, informed the magazine of the error.

[3] Following World War II, Sigma Pi benefited from increased college enrollments under the GI Bill.

[11][5] Beta-Kappa chapter at Arizona State University, chartered in 1951, was unique for having founder James Thompson Kingsbury assist in its founding.

In 1988, the fraternity received the Rose Hill Farmstead from the family of founder George Martin Patterson and sold the property to the Sigma Pi Educational Foundation in 1992.

Sigma Pi Fraternity promotes five basic ideals or pillars:[20] The Sigma Pi Creed expresses the fraternity's ideals: I Believe in Sigma Pi, a Fellowship of kindred minds, united in Brotherhood to advance Truth and Justice, to promote Scholarship, to encourage Chivalry, to diffuse Culture, and to develop Character, in the Service of God and Man, and I will strive to make real the Fraternity's ideals in my own daily life.

[5] In 2010, Sigma Pi shifted the Grand Council to a Board of Governors model, focusing on policy creation, while the Executive Office Staff handles implementation.

Generally Sigma Pi requires members to be in good academic standing and be active in the campus community.

[3] Sigma Pi encourages a fraternal culture that promotes its ideals by philanthropic events for its members and the communities in which its chapters are located.

Each chapter is required to complete regular philanthropy events and participate in Sigma Pi's Altruistic Campus Experience (ACE).

Finally, Sigma Pi's Educational Fund provides assistance to students to cover the costs of college tuition.

In doing so Sigma Pi hopes to turn tragedies into rallying points to help promote and encourage a cause that has affected brothers as well as their families.

At this time, Sigma Pi focuses its philanthropic efforts on two organizations for the following two years; the Amazing Day Foundation, and Donate Life America.

Furthermore, Sigma Pi requires each individual chapter to sponsor philanthropy events throughout the academic school year.

Sigma Pi even encourages chapters to participate in Philanthropy events that occur during school breaks and summers.

At the 2012 Convocation in San Antonio, Texas, Sigma Pi unanimously voted to collect 5 dollars per undergraduate member per year specifically designated for the educational foundation.

The project is the first fraternity or sorority campus service program for chapters specifically designed to benefit their host institutions.

In March 2012, the Beta chapter at Indiana University released a 10-minute short film titled ‘FRATLINE: The Hazing Barrier’ which was banned by the Inter Fraternity Council and dean of students.

Attention was drawn to the film (which was released on YouTube) after it received nearly 30,000 views in a week and depicted a hazing obsessed pledge master named Adam.

On March 1, 2016 - nine months prior to the release of these photos - the Grand Council of Sigma Pi revoked the chapter's charter due to "violations of both Fraternity and FIPG risk management policies.

Shortly after the chapter withdrew from the Greek community, the University of Missouri banned Sigma Pi from campus.

This was the colony's first offense, though a prior iteration of Sigma Pi on this campus faced its own risk management problems.

"[32] In mid-November 2018, a former pledge was found unresponsive and later pronounced dead at an unofficial annex house to Ohio University's Epsilon chapter of Sigma Pi.