Founded in 1871, the Philosophical Society of Washington is the oldest scientific society in Washington, D.C. It continues today as PSW Science. Since 1887, the Society has met regularly in the assembly hall of the Cosmos Club. In the Club's present location since 1951, the assembly hall is now called the John Wesley Powell auditorium. Meetings are roughly every other Friday, except in the summer. Meetings are free and open to the public. A lecture is given by a scientist at each meeting.