- October 19, 1850- Alpha Chapter founded at the University of Pennsylvania by Samuel Brown Wylie Mitchell.
- August 9, 1854- The Fraternity holds its fist convention, in Philadelphia.
- 1857- Alpha Chapter publishes and distributes the Phi Kappa Sigma Magazine and the Fraternity becomes the first fraternity to publish a fraternity-wide newspaper or magazine for its members.
- 1859- James W. Barrow established the Phi Kappa Sigma Male College in Monticello, Arkansas- the first institution of higher learning in the state, making Phi Kappa Sigma the only Fraternity ever to have had a college named in its honor.
- 1869- The first regularly constituted alumni chapter is organized in New York.
- 1869- The Grand Chapter was established at the Fraternity's convention of this year, making Phi Kappa Sigma the first fraternity to organize a Grand Chapter and establish a democratic system of government based on chapter representation.
- 1869- The first Grand Alpha, John Clark Sims, is named.
- 1888- Alpha Chapter establishes the Samuel Brown Wylie Mitchell Prize in English Literature at the University of Pennsylvania, representing the first scholastic award offered by a fraternity in any American college or university.
- 1895- The Fraternity establishes itself as an International Fraternity with the establishment of Alpha Beta Chapter at the University of Toronto.
- 1898-1906- Grand Alpha James Hartley Merrick implements the Chapter Advisor system.
- 1906- The Fraternity's Chapter Rolls reaches 30.
- 1907- The Phi Kappa Sigma Endowment Fund is established.
- 1909- The Fraternity becomes a charter member of the National Inter-Fraternity Conference (NIC).
- 1915- The Fraternity establishes a General Headquarters in Philadelphia to improve organizational operations.
- 1947- James B. Fox (Alpha, '44) is named as the Fraternity's first full-time Executive Secretary.
- 1948- L. Jerrold Wells (Alpha Omega, '48) is named as the Fraternity's first travelling Field Secretary.
- 1953- The Phi Kappa Sigma Educational Fund is created.
- 1977- U.S. Supreme Court Justice, Lewis F. Powell (Alpha Alpha, '29), is named the Fraternity's first Alumnus-of-the-Year.
- 1981- The General Headquarters moves to Valley Forge, PA.
- 1982- The Phi Kappa Sigma Foundation is established.
- October 20, 1994- The Fraternity purchases a headquarters building in Chester Springs, PA.
- July 1, 2000- The Fraternity moves forward with its substance-free housing initiative.
- July 2000- at the 90th Grand Chapter in Philadelphia, PA, the Fraternity adopted The Statement of Core Values, reaffirming Phi Kappa Sigma's commitment to its founding principles.
- August 16, 2000- The Fraternity proudly celebrates the sesquicentennial (150th) anniversary of its founding date.
- January 2001- Phi Kappa Sigma held the first Men of Honor leadership development program.
- July 2004- at the 92nd Grand Chapter in Chicago, IL, the Fraternity adopted the Doctrine of Excellence, providing our membership with a roadmap to excel in todays fraternal community.