[1][2] On May 7, 1844, several residents of northwest Washington who had previously attended services at St. John's Episcopal Church in the Lafayette Square neighborhood met to begin forming their own parish.

In accordance with her wishes, Mr. Van Ness donated land on H Street NW between 9th and 10th to Ascension Parish, and the cornerstone was laid September 5, 1844.

As many parishioners had friends and relatives in both the Northern and Southern states, their feelings and loyalties boiled over in the church during the period leading to and during the Civil War.

This division was evident in the clerical ranks also as the rector, Mr Pinkney, sympathized with the South while Maryland Bishop William Whittingham was a Unionist.

In March 1862, Bishop Whittingham requested parishes to say a special prayer of thanksgiving for the late (Union) victories; Mr. Pinkney refused.

The Saturday following Pinkney's refusal, Washington's provost marshal notified him that the authorise would assume control of the church to prevent a disturbance.

Ascension became a military hospital to house casualties from the Peninsula Campaign, as did Epiphany Church and Holy Trinity in Washington.

Although the official designation ceased, the church continued to be used as the pro-cathedral for important occasions until 1912 while the Washington National Cathedral was under construction.

This downturn continued through 1947, and the diocese considered selling the building to another congregation when the Vestry received a proposal to merge from St. Agnes Church, located at 46 Q Street NW.

The rear balcony became the new location for the three manual instrument, which had been constructed from spare pipework from the discarded Roosevelt and surplus mechanical parts.

Moller retained only two ranks of pipes from the original Roosevelt (the Swell Gedeckt 8' and the same division's Spitz Flute 2’) and supplied entirely new structure, winding, console, and pipework for its opus 11615.

In addition, it became mechanically unreliable; and since the Moller firm had ceased to exist in 1989, the parish had no recourse other than to commission a repair and rebuilding of the instrument.

The parish organ committee selected the firm of Orgues Létourneau of Sainte-Hyacinthe, Québec and engaged a design consultant, Charles Nazarian of Gloucester, Massachusetts.

Thanks to the close collaboration between Mr. Nazarian and the designers on the staff of Orgues Létourneau, the plan for the Church of the Ascension and Saint Agnes evolved into the twin cases of American red oak framing the central window.