Saint Ambrose was initially in the parish of St. Mary of the Mills in Laurel as part of the territory administered by Archbishop John Carroll of Baltimore. When Saint Jerome in Hyattsville was established, our parish territory became part of that parish, and beginning in 1883, a priest would visit this area to minister to Catholics. In 1886, a wooden chapel was built on property donated by the Wilson family, giving Catholics of Old Landover and its surrounds a more permanent arrangement. The oldest document testifying to the existence of Saint Ambrose is a letter dated July 12, 1886 from Cardinal James Gibbons, Archbishop of Baltimore, to the pastor of Saint Jerome parish, Father Walker Caughey. The letter gave permission to set up the Stations of the Cross.

The little wooden chapel was used to celebrate Holy Mass and for the Sacraments of Initiation and Forgiveness until January 1960 when it was demolished and the remains burned to make way for the John Hanson Highway. Ground was broken in November 1960 for the new and magnificent Saint Ambrose Church on the hilltop where it now stands. The original bell tower has survived. In this bell tower, which is now being used as a small chapel, there are three of the original church windows. There are also two little windows showing a small angel caressing a large beehive. The double doors, used as the entrance, are the original inside doors of the church. This chapel, still in our parish, rests on the private property of the Rogers Family at Beall's Pleasure.

The Archbishop of Washington, Patrick O'Boyle, established the independent parish of Saint Ambrose in 1948 when he separated it from its parent church in Hyattsville. He sent Father Ronald Fannon to be the first pastor and Father Fannon worked untiringly, building upon the foundations of true Catholicism. Monsignor Philip Brown continued the work after Father Fannon's death in 1954. The parish prospered under their guidance and from their hard work and the work of all those who helped them.

Timeline of selected events

1950       April 23: Ground-breaking for the new parish building
                October 1: The convent opens
                October 2: First day of school, with only the first four grades
                November 12: Dedication of the auditorium, school, and convent
 
1951       January: Father Leo Cody comes to assist Father Fannon
                June: Father George Ellis, just ordained, arrives as Assistant
                September: The new rectory opens; the school is opened with a full complement of eight grades
 
1954       December 9: Father Fannon dies
 
1955       January: Father Philip Brown arrives to assume the Pastorate
 
1956       September: Eight classrooms are added to the school, bringing the total number of rooms to sixteen
 
1960       Permission is granted to begin the preliminary work toward building and financing a church building
                March 6: The Most Reverend Philip M. Hannan breaks ground
                November 12: Excavation begins
 
1961       December 17: The building is blessed and set apart for worship by Archbishop O’Boyle
 
1999       December 4: New altar is installed and dedicated by James Cardinal Hickey