Holy Trinity was born November 11, 1924 and was briefly called St. Peter's.   However, to avoid confusion with St. Peter's Episcopal Church, the name was changed to Holy Trinity.   Father Patrick O'Dwyer became the pastorate on March 1, 1925 performing the first baptism in April and first marriage in September.

 The church functions were held in the Barton Hill Theater on 221 Pacific Avenue until Father Joseph Meehan became pastor in 1926 when the services were transferred to a vacant store at 441 Santa Cruz. In 1927 property on O'Farrell Street was purchased for $8,000.

 Ground was broken for Holy Trinity Church in January of 1927 and the building was dedicated on October 2, 1927.   Because of the great depression and the parish debt, the financial responsibility for the parish was to given to Mary Star of the Sea.

 In September of 1935 a religious school for public school children was started. The convent opened in a converted house, which had been purchased in 1927 when the church was built.   In 1946 Holy Trinity was declared an independent parish with Father George Gallagher as pastor.   A rectory was purchased and the church and auditorium were renovated.

 In 1950 land was purchased for a school with ground breaking in March and the dedication was held in November of 1951 with classroom expansions in 1956 & 57.

 Property on Hanford was made into a convent for the Sisters of the Presentation.   During the 50's, the rectory became part of the church campus.   In 1960, population increases resulted in Holy Trinity re-locating to 1292 West Santa Cruz and the old church became the Chapel of San Pedro and was raised to parish status on January 21, 1966 and is now St. Peter's.   Prior to this, ground breaking began in 1959 for a new church and was completed in 1960 and dedicated was held on April 29, 1962.   The United Steel Workers contributed the beautiful sounding bells to the new church.

 On February 2, 1979 Father Thomas J. Glynn became the pastor.   In 1990 the Parish began a major fund raising campaign for a new parish center.   The Center opened in 1994. Early in 2000 plans were formulated for a fund raising initiative to remodel the Church, remodel as well as expand the school, and move the rectory to a new location.

 Construction began in the Spring and was completed in the fall of 2002.  The dedication was held October 13, 2002 with Cardinal Roger Mahony presiding.

June 2004 Father Tom retired and Father Joseph Brennan became Holy Trinity's pastor July 1, 2004.