Hamilton said prisons are an area ripe for union expansion.
"We believe these correctional facilities in particular have a real meaningful future in the state of Pennsylvania because they're largely unrepresented in many, many areas," he said.
Leaders of the state Fraternal Order of Police attended the news conference and said afterward that they applaud the Teamsters' attempt to expand guard unions.
"But when it comes to the representation of police officers, we strongly believe the only representation that can be given is by police officers themselves," said Pennsylvania FOP president Les Neri.
Neri said that although the Teamsters represent many smaller police departments in Western Pennsylvania, the FOP would continue to dominate urban departments and most of Southeast Pennsylvania.
"Imagine a Teamster police officer pulling over a Teamster truck driver," Neri said, adding that the appearance of a conflict of interest justifies keeping police officers separate.
Carl Bailey, a former McKeesport, Pa., police detective who leads Teamsters Local 205 outside Pittsburgh, said he respects the FOP. "I wish we had a better relationship because I think we're all fighting for the same things," he said.
However, Bailey doesn't see police departments as FOP territory. In fact, he said, his staff was working Thursday to bring in another department from Fayette County.
"Hopefully that'll be my 51st police department coming onto my local," he said. "It's a growing industry."
Teamsters Local 384 organizer Chris O'Donnell said the Teamsters "need to get more of a presence" in correctional facilities across the state.
"It's very prevalent in Harrisburg and the western part of the state," he said, but there's a "dire need" in Montgomery County and other areas.
Teamsters leaders said there was no effort yet to organize prison guards in Chester County or Delaware County, where two African American guards are suing the operator of the county facility for alleged racial discrimination.