Six students at Miami University - Robert Thompson Drake, John Wolfe Lindley, Robert Morrison, Andrew Watts Rodgers, Ardivan Walker Rodgers, and John McMillan Wilson - founded Phi Delta Theta on 26 December 1848. Rapid and widespread growth immediately followed and continued for more than half a century. By 1940, Phi Delta Theta could boast that it had more active chapters that were over fifty years old than any other fraternity in the country.

In 1898 and 1899, Penn's Zeta chapter built its Gothic-style fraternity house at the southwest corner of 34th and Walnut Streets (re-adapted today as the Jaffe History of Art Building). In 1925, Phi Delta Theta built a second house at 3700 Locust Walk, this time in the Colonial Revival style. It remains there today.