What date was the 2nd quaker city rock festival at the spectrum Janis Joplin mobey grape vanilla fudge buddy guy chambers bros?

The 2nd Quaker City Rock Festival took place on July 28, 1968, at the Spectrum in Philadelphia. The lineup featured notable artists including Janis Joplin, Moby Grape, Vanilla Fudge, Buddy Guy, and the Chambers Brothers. This festival was part of the vibrant Rock Music scene of the late 1960s.