If you are researching the Germantown area, the following microfilm sources may be of interest to you. If you know of other film sources that cover or identify the Germantown area and are not identified here, would appreciate knowing of them.
LDS/FHL = Church of the Latter Day Saints, Family History Library
Some general comments regarding the early 1840-1850 records.
During this period, especially the 1840s, the Washington County area was viewed as missionary territory. That is, the missionary on his trusty horse would travel through the area and minister the word and perform marriages and baptisms. From a civil standpoint, only marriage were important and these may have been recorded in the then court house. From a religious standpoint, baptisms, marriages and burials may have been recorded but the question is where? In this wilderness there were congregations but did they maintain registers and if they did, was a registration actually made?
Looking at the Catholic church for example, the first religious in Washington County was Father Michael Heiss whose home base was in Milwaukee. So in the years 1844 to 1846, all his registrations were recorded in the books of the Cathedral of St. Peter the Apostle. But before Father Hess we have firstly Father O'Kelly who was in the area supposedly since 1838 although his registrations do not begin until 1840 and Father Kundig who arrived in 1842. So from 1840 to 1846 there was only one church in Milwaukee, first called St. Luke and after 1844 the Cathedral of St. Peter the Apostle. During these years, if you are looking for a Catholic registration, the only place it can be is in the books of the Cathedral of St. Peter the Apostle.
During the years of 1838 to 1840, the missionary Father O'Kelly was operating out of the Detroit Diocese. Should there be any registration, they could only be found in the records of the Detroit Diocese.
In 1846-1847 we have Father Obermueller operating out of St. Boniface in Goldenthal and Father Meyer operating out of St. Anthony the Hermit in Fussville, ministered to the then Washington County. St. Francis Xavier in Grafton and St. Francis Borgia in Cedarburg were also recording registrations. So during this period, you might look at the books of St. Boniface, St. Francis Xavier, St. Francis Borgia, or St. Anthony.
Marriages were recorded at the Court House in Port Washington.
In 1849-1852 we have Holy Cross in Holy Cross, St. Lawrence in St. Lawrence, St. Mathias in Nabob, St. Mary of the Lake in Belgium, St. Bridget in Jackson, St. James in Mequon, St. Matthew in Neosho, Mother of Sorrows in Little Kohler, St. Mary in Port Washington, and St. Stephen in Port Washington. As this was still considered a missionary period, those elusive recordings would have to be within these parish registrations.
That leaves us with Father Caspar Rehrl who ministered in the area from 1852 to 1878. During this period he performed registrations for St. Bridget (Wayne), St. Matthew (Neosho), Holy Trinity (Newburg), St. Kilian (St. Kilian), St. John of God (Farmington), St. Michael (St. Michael), Mother of Sorrows (Little Kohler), St. Anthony (Allenton), SS Peter and Paul (Nenno), St. Peter the Apostle (Trenton), St. Lawrence (St. Lawrence), St. Theresa (Theresa), and St. Martin (Ashford). Some of his registrations were not assigned to any particular parish and were recorded under his name for Washington County 1855-1865. See LDS-FHL film 1887361.
For the Christ Evangelical and Reformed Church in Dheinsville, they report the early registrations were lost in 1861. In the latter half of the 20th century, the congregation attempted to add the lost entries back, as best they could, from memory. It would seem, from what we are now hearing, these early recording may not have been completely lost. You might check with the Germantown Historical Society.