Speakers at the Keystone Cannabis Reform Rally on Monday urged the use of the drug for medical purposes, the production of industrial hemp and the decriminalization of recreational marijuana.
A bill pending in a state Senate committee would permit the use of marijuana for medical purposes.
The National Conference of State Legislatures says 20 states and Washington, D.C., currently allow for comprehensive public medical marijuana programs.
The bill's prospects are uncertain, and Gov. Tom Corbett has signaled his general opposition. His spokesman says that if federal drug regulators decide the use of a marijuana byproduct is safe and effective for patients, he would review their conclusions.