Spencer came to Kamloops, B.C. from Ontario in 1899 and set up a photography studio on Victoria Street at 2nd Avenue — the same location as the CBC Kamloops studio today.
Some of her most well known photos are the iconic images of notorious train robber Billy Miner when he was captured in Kamloops, and of the court case that followed.
"It's like you're seeing the courtroom drama before your eyes. You can almost see people holding their breath as these intense speeches are being made," museum supervisor Julia Cyr told Daybreak Kamloops' Doug Herbert.
"You can feel the tension in the room."
Spencer didn't just take photos of famous criminals — she also captured the everyday life and faces of Kamloops from the turn of the 20th century.
"She was taking photographs of people of all ethnicities, of all class, of all religion. She was very interested in family, community and she was capturing people who were somewhat eccentric too in town," said Cyr.
"She was also looking at these photographs in terms of composition. What could she do that was introducing different light and technique? So she had an artistry to her."
The exhibit runs at the Kamloops Museum until June 30.
To hear the full interview with Julia Cyr, click the audio labelled: Mary Spencer's photography.