The blaze did not damage the inside of the building - or the soul of the theater, which has entertained audiences since the early 1950s.
"Riverside is known by our slogan 'the city of arts and innovation.' This building was raised in 1953 and we were the only game in town then so we kind of think that we were the beginning of the arts movement in Riverside," said Lynne Ennis, vice president of the theater board.
Ennis says even though valuable stage equipment was destroyed, a theater production set to debut this weekend will go on as planned.
It is called "Oz" and Ennis says the show requires a cluttered set. That has been easy given their situation after the fire.
"It was filled with vintage furniture pieces we used for period shows," said Ennis. "Lots of props! They pulled quite a bit of it out because they're burning and over here we saw tons of furniture that was burnt to a crisp and no longer usable."
Arson investigators are planning to interview someone who they have identified as a person of interest in connection with the fire.
Ennis is thankful for the charitable hearts in the community. She is hoping donations will keep coming in to get the theater back on its feet, and better than ever.