Pi Kappa Alpha is an international, secret, social fraternity. It was founded at Room 47 West Range at the University of Virginia , on March 1st, 1868. It was established by the following Founding Fathers: Frederick Southgate Taylor, James Benjamin Sclater,Julian Edward Wood, Littleton Waller Tazewell, Robertson Howard, and William Alexander. The essence of the Founder's vision can be found in the Preamble:

"For the establishment of friendship on a firmer and more lasting basis;
for the promotion of brotherly love and kind feeling;
for the mutual benefit and advancement of the interests of those with whom we sympathize and deem worthy of our regard;
We have resolved to form a Fraternity, believing that, thus we can most successfully accomplish our object."

The Beta Sigma Chapter at Carnegie Mellon University was founded on Dec. 5th 1921. It was formed after the local fraternity Zeta Delta petitioned to become a chapter of Pi Kappa Alpha. See more information on the history of the Beta Sigma Chapter here.

Links:

Pi Kappa Alpha National: http://www.pikes.org
Pi Kappa Alpha Beta Sigma Chapter: http://www.cmupikes.org