In 1882 John Bolton, the Irish land developer who plotted Rocklin's original town site, donated an oak-framed lot to Rocklin's Catholics for our City's first Catholic Church. Construction started shortly after the Bolton donation and Gold Rush era Archbishop Joseph Alemany of the San Francisco Archdiocese dedicated the newly constructed church as Saint Mary's of the Assumption Catholic Church on August 13, 1883.

The church was at 5420 Front Street, on a knoll overlooking the transcontinental railroad tracks about 100 yards to the east.

Saint Mary's served Rocklin Catholics throughout the remainder of the 19th century and it survived the fires that obliterated downtown Rocklin in the early 20th century. But a declining granite industry and adverse economic effects of the Great Depression depopulated Rocklin and closed the church in 1933. Woodpeckers and foul weather toppled Saint Mary's steeple in 1937. 
In 1946 Saint Mary's reopened for 9:30am Sunday masses, but in the ensuing years it often operated only as a satellite of parishes in Roseville and Lincoln.

In 1978, Parishioners gave Saint Mary's a facelift and performed extensive repairs but the church continued to fray with age.

In 1981 Fr. Michael Dillon assumed leadership at Saint Mary's, renamed the parish Saints Peter and Paul and moved the congregation to a new church on Granite Drive. Dillon held the last mass at Saint Mary's on December 23, 1983. "Saint Mary's seated 80 people" said Dillon. "It was not nearly large enough for fast growing Rocklin". Dillon also remembers the inconveniences of an obsolete building. "The windows had to be open to circulate air in the warm months," he said "and I spent a lot of time swatting horseflies trespassing at mass from the neighbor's corral".
In 1986 the Diocese of Sacramento sold the church to The Church of Religious Science, which conducted services there until 1996. That year the mortgage holder, Lois Caprile of Washington, foreclosed and offered the church, including the oak-framed lot, to the City of Rocklin as a gift. But the city refused her offer because of the building's poor condition. Caprile then gave the church, including the lot, to a Baptist congregation instead.

Neighbors in the Front Street area can't remember that the Baptists ever held services in the church but in 2001 the Baptists sold the church to Electrical Maintenance Consultants who applied to the city to demolish it. EMC needed room to expand their business. 

The Rocklin Historical Society  heard of the church's plight from the city staff who processed the demolition application. Recognizing the church's historical significance, RHS immediately started negotiations with EMC to try to save it.  In 2005 EMC offered the church to RHS as a gift with the proviso that it be moved quickly out of EMC's intended expansion area.

RHS accepted and on September 17, 2005 RHS moved the church 1000 feet north to be restored and to become the centerpiece of Heritage Park at Front Street and Rocklin Road. The park is a joint City of Rocklin and RHS project to beautify Rocklin's railroad corridor with building restorations and new landscaping.

RHS completed the restoration in September 2007 and renamed the building "Old Saint Mary's Chapel"
RHS has saved Saint Mary's to become a key landmark in the restoration of downtown Rocklin.