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The theatre was established by local theatre artists in 1989. It served as an arts collective serving local and regional theatre, visual arts and musical artists with a focus on emerging artists. The space was primarily a performance space "black box" style theatre.
As a "collective" the space was run by a revolving membership of artists, some of whom have gone on to open larger, more main-stream theatres in Canada, including Robert Winslow, one of the space's founding members who in 1995 started Fourth Line Theatre in Millbrook, Ontario. Other theatre alumni now work for large arts organizations around Canada.
The Union Theatre was located at 188 1/2 Hunter Street West in an old Coffin Factory. The space closed its doors on Hunter Street in 1995 and moved to a new home in Peterborough in 1996 where they only remained for one year. In 2006 a group of local artists from the Union Collective began work on opening a new theatre space with the same artist-run focus. The Theatre Users Group formed in the summer of 2006 under the acronym "T.H.U.G." 
- The space ran monthly "Writers in the Round" songwriter shows where Canadian songwriters would share their newest works "in the round" with four or five other artists in front of a live audience.
- Weekly "Improv Soaps" were developed using serial-style episodic story lines featuring reoccurring characters. Its series "Hurricane Ridge" was loosely based on the Twin Peaks television show.
- Shows sought funding through a number of sources including government grants and student-based funding from Theatre Trent (Trent University).
The Union Theatre is noted in Anne Russell's (Peterborough, Ontario, Canada: Broadview Press, 1994) edition of Aphra Behn's The Rover as one of a selection of small theatres in the 20th century to produce the rarely-produced Restoration comedy script.
Collective members met bi-weekly to decide issues of space use, booking of shows, space upkeep and funding. Since the space was a not-for-profit organization it relied completely on the 50% of its door proceeds for its success. The Union Theatre received funding from the City of Peterborough's Arts and Culture committee as well as from both The Canada Council and The Ontario Arts Council.
- Peterborough Examiner, May 8, 1996
- Peterborough Examiner July 14, 2006, pB4.
- Peterborough Examiner January 18, 2001.
- Peterborough Examiner January 21, 2006.
- Peterborough Examiner July 2, 2005, p. B8.