C. S. Haskell [Haskell Pipe Organ Manufacturing Co.]
1915

The First Presbyterian Church, Washington DC (aka Old First) was located at 4-1/2 St NW (John Marshall Place) now John Marshall Park. The building which the Knauff organ was installed was built in 1859. The congregation merged with Covenant Presbyterian, then on Connecticut Ave. The merger took place in 1929-1930. Soon after the old First Pres was demolished.

The First United Presbyterian Church, (aka Wallace Memorial) located at New Hampshire Ave & Randolph Street was part of the a conservative branch of Presbyterians, then known as United Presbyterians as they included Associate Presbyterians and Associated Reformed congregations. The present day United Presbyterians were part of main-line Presbyterians who joined together in the 1950s or 60s. The building at New Hampshire & Randolph is now occupied by an African American Baptist congregation. It was built for the United Presbyterians in 1915. This writer serviced the 1989-90s Moller organ, in the late 1990s.
source info - Washington Evening Star 3/6/1915 pg 18 & March 6, 1915 pg 18
A large article about the renovation of the 1st Presbyterian Church, Washington (Old First) is found in The Evening Star Nov 19, 1892 pg 14 with a drawing of the new organ balcony and facade of the new Knauff organ.

Also confirmed from listing published by the firm in The Diapason, February, 1915.

The church unerwent two name changes, in 1915 was renamed Wallace Memorial Presbyterian Church and later became First Baptist Church.

Identified from information in the Evening star (Washington, D.C.), March 6, 1915, Part 2, "In the Realm of Higher Things" section. An announcement that "First UNited Presbyterian Church will be known after dedication tomorrow as Wallace Memorial"..."Name to undergo change in memory of Dr. A. G. Wallace". In the article with detailed description fo the church, architecture and furnishings is mention of the organ: "...the church is equipped with a Haskell pipe organ."