The first general fraternity we have records of was organized in 1750 at the College of William and Mary in Willamsburg, Virginia. Known as the "Flat Hat Club", the members met periodically in an upper room of the Raleigh Tavern, and over a bowl of punch, their laughter reportedly shook the house. Thomas Jefferson, author of the US Declaration of Independence and third President of the United States, was a student member of this club.

The first Greek-letter society came into being because a student had been refused admission into a William and Mary organization known as PDA. The PDA club was supposedly a literary society but had long lost those purposes. The rejected man was a superior Greek scholar. With four friends, he organized a society of his own, using Greek letters to name it: Phi Beta Kappa.

The first meeting of Phi Beta Kappa took place on December 5, 1776. It was a secret meeting, for the faculty of William and Mary at the time did not approve of its students discussing the pressing issues of the day and possibly straying too far from accepted beliefs. So Phi Beta Kappa developed appropriate signals of challenge and recognition. And they met weekly at the site of American patriot Patrick Henry's "give me liberty or give me death" speech in the Apollo room of the Raleigh Tavern in Willamsburg.

They discussed "whether anything is more dangerous to civil liberty in a free state than a standing army in time of peace" (the Americans having declared their independence from Britain in July 1776) and dozens of other controversial topics. Each topic was argued according to Phi Beta Kappa rules so that each man contributed his full share of the discussion.

After two years, Phi Beta Kappa felt that other campuses should share its good idea that the higher education experience give proper consideration to prepare the student for his future responsibilities... by preparing him socially. Chapters were founded at several American colleges. As time went on, Phi Beta Kappa became purely intellectual in its aims, though the original cardinal principles were "literature, morality and friendship." During anti-secret movements of the 1830s, Phi Beta Kappa, the society voluntarily revealed its once secret Greek name, "Filosofia Bion Kuberneqes" (Philosophia Bios Kybernethes), or "Philosophy (is the) guide to life". Since that time, Phi Beta Kappa has become a scholastic honorary society and today recognizes men and women, who, as undergraduates, show superior achievement in academics in more than 184 college campuses in America.

The secret grip and ritual, the distinctive badge, the use of Greek letters -- all were used by Phi Beta Kappa and were adopted by subsequent Greek letter fraternities and sororities. But the important legacies of Phi Beta Kappa are these: high moral ideals, scholastic advancement, and the friendship of one Brother with another.

On the campus of Union College in Schenectady, New York, the decline of a military marching club left a void in student life in the fall of 1825. So a group of students, including several members of Phi Beta Kappa, organized Kappa Alpha Society on November 26, 1825. This Greek-letter social fraternity continues to this day.

Due to its secrecy, students and faculty alike opposed Kappa Alpha Society, but other students admired the organization and formed Sigma Phi and Delta Phi in 1827 as rivals of Kappa Alpha. Kappa Alpha Society, Sigma Phi and Delta Phi formed the "Union Triad" which exists today. Eventually, a total of six fraternities were founded at Union College, which is why the college is recognized as the "Mother of Fraternities".

Sigma Phi founded a second chapter at Hamilton College, Clinton, New York. Seeking an alternative to two bitterly fighting literary societies, some Hamilton students took inspiration from the local Sigma Phi chapter and founded another Greek-letter society, Alpha Delta Phi. Alpha Delta Phi was on the move before long and founded its second chapter west of the Allegheny Mountains at Miami University in Oxford, Ohio, in 1833.

In 1834, students at Willams College in Massachusetts founded Delta Upsilon as an open (non-secret) society which continues to this day.

The first ten college social fraternities founded were:

Phi Beta Kappa, 1776
Kappa Alpha Society, 1825
Sigma Phi, 1827
Delta Phi, 1827
Alpha Delta Phi, 1832
Psi Upsilon, 1833
Delta Upsilon, 1834
Beta Theta Pi, 1839
Chi Psi, 1841
Delta Kappa Epsilon, 1844
Alpha Sigma Phi, 1845

In 1839, John Reilly Knox was a prominent member of a literary society at Miami University in Oxford, Ohio in a "rather bitter fight" against Alpha Delta Phi. He admired the spirit and organization of Alpha Delta Phi members, but imagined a society of "good without the ingredient of evil" and founded Beta Theta Pi, the first member of what was to become the "Miami Triad". Phi Delta Theta, and Sigma Chi, founded in 1848 and 1855 are the other two members of the "Miami Triad".

Establishing a pattern, most of the pre-Civil War (1861-1865) fraternities were founded in specific imitation or of opposition to other existing fraternities. After the Civil War, new Greek-letter organizations were founded in the South. Some of the fraternities founded during this period were:

Chi Phi, 1824 (merger of two societies with the same name, one founded earlier in 1824, before Kappa Alpha Society)
Theta Delta Chi, 1847
Zeta Psi, 1847
Phi Gamma Delta, 1848
Phi Kappa Sigma, 1850
Phi Kappa Psi, 1852
Alpha Tau Omega, 1854
Sigma Alpha Epsilon, 1856
Delta Tau Delta, 1858
Kappa Alpha Order, 1865 (note: this is different and separate from the earlier Kappa Alpha Society.)
Pi Kappa Alpha, 1868
Sigma Nu, 1869
Kappa Sigma, 1869

By 1900, there were thirty-seven fraternities in existence. Other fraternities have come into existence since then. There are over 60 existing Greek-letter fraternities today. Some fraternities, though considered to be Greek-letter in scope, do not have Greek-letter names. These are:

Acacia, 1904
FarmHouse, 1905
Triangle, 1907

On May 15, 1851 at Wesleyan Female College in Macon, Georgia, a group of women founded the Adelphean Society, which later adopted the Greek letters Alpha Delta Pi. 1852 saw the founding of the Philomathean Society at the same college, which adopted the letters Phi Mu.  In 1870, Kappa Alpha Theta became the first Greek-letter women's fraternity and was founded at DePauw University, Greencastle, Indiana. The term "sorority" actually was first used by Gamma Phi Beta, founded in 1874 ant Syracuse University, New York and is used to describe women's Greek-letter societies, though many of the earlier women's societies use the term "fraternity" in their name. Today there are over 25 national sororities in existence, all members of the National Panhellenic Council (NPC).