Milestones in the History of St. Thomas The Apostle Parish
| 1720s | Mass in Willcox family homestead, at Walters Road (now Ivy Mills Road) and Polecat Road, “since the 1720s.” English Jesuit missionaries from Bohemia, Maryland. |
| 1729 | Parish founded. Mass held regularly at Willcox homestead. |
| 1837 | Saint Mary’s Chapel built as part of new Willcox mansion. |
| 1852 | Cornerstone of new church building blessed by St. John Neumann, Bishop of Philadelphia. Parish membership: 500-600 persons. |
| 1860 | Bell installed in steeple. |
| 1874 | Rectory built, replaced 1858 rectory which had burned in 1873. |
| 1897 | First Country Fair. Proceeds support 1898 renovation. |
| 1898- 1900 | Church building renovations, including installation of stained glass windows. |
| 1936- 1938 | Further renovations in church building including removal of exterior stucco, installation of side altars and present interior lighting. |
| 1957 | Elementary school and convent built. |
| 1966 | School building enlarged. |
| 1973- 1974 | Church building renovations, including present wainscoting. |
| 1991 | New, larger church building dedicated in June. Parish membership: over 1200 families. |
| 1997 | New Rectory completed |
| 2000 | Education Center dedicated. Convent razed. Parish membership: 2200 families. |
| 2001 | Second Floor added to School |
| 2007 | Recreation Center completed |
| 2013 | Air Conditioning installed in 1852 Church. Parish membership: 2800 families. |