I’ve been working on piecing together the earliest history of churches in my area and in the process have acquired a number of digital maps of the area. Putting them here in chronological order may be of some benefit to later explaining the history.
The following maps are from 1769, 1780, 1829, 1851, 1860, 1875, 1898, 1903, 1910, and today.
This first map, from 1769, is merely a section of a larger map. It has the unnamed creek through Unionville misnamed as “Rutkers Kill.” Later Rutgers Kill or Creek is the name given to the larger creek just to the north. There are no residents shown in the area at this time.
The 1780 map now has “Rutkers Creek” labelled correctly. The “Drowned Land” are shown. These today are drained and are the excellent farmland known as the “Black Dirt Region.” The first resident near present Unionville is shown as “S. Meekers” just south of the creek. Some roads are now shown as well. It was on Samuel Meeker’s land that the first Meeting House was built.
The 1829 map is notable for being the first to have Unionville Church and Westtown Church shown, even if they are unnamed. While the churches indicate the approximate centers of both Unionville and Westtown village, the “Unionville P.O” and “Westtown P.O.” are, for reasons unknown to me, shown in locations that do not match the villages. 
In 1851 we find that major roads are built but many of the streets in Unionville are not yet in existence. This map shows just the New York side of the border and is the first to show many residences. The Orange Church is not Meeker’s Meeting House, but the location of the Orange Baptist Church (1822-1852) before they relocated into the village of Unionville, later disbanding entirely. By this time the “P. Church” (Unionville Presbyterian Church) was built. Further up (not shown here), the Westtown Church is called “O.S.P” for Old School Presbyterian. This is interesting because the Unionville Church was New School but is not labled as N.S.P. 
The next map, from 1860, mostly shows just the New Jersey side of the border. Samuel Meeker’s property is now in the possession of S. Christie. Later it will be the Harry Christie farm. 
The 1875 Minisink Map covers the whole town. This is a clipping of just the Unionville section. Most of the village streets are built. 
A detailed map then of Unionville (shown here in 2 parts) was also made in 1875. 
The detailed 1898 and 1910 fire insurance maps are too large to upload here.
And then I have a clipping from the 1903 map. 
Lastly, the area I’m researching today. I’ve now figured out fairly precisely the location of the early meeting house. That is, I know who owns the property today. Whether there are any remains of a foundation or anything else, I have yet to explore. 
Edit 2/22/2022
This 1828 Map of New Jersey by Thomas Gordon appears to have a “forge” (as indicated by the circle-cross symbol) shown near Meeker’s meeting house. While a tannery is said to have been there at a later point, I don’t know of any forge. Should it rather have been a cemetery marker?
