There is an entry fee to come into Fort Gaines, but it is well worth it in our opinion because there is so much to see here.
This stone survey Monument was erected in 1847 by C&GS Superintendent A. D. Bache, who was surveying the Dauphin Island Base Line as part of the Eastern Oblique Arc survey of 1847. His work surveying the line was destroyed by storms that washed away most of the monuments he set by 1883, but this post was found and is preserved today inside Fort Gaines.
From the NOAA Photo Library: (
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"Granite obelisk used to designate one of the end points of the baseline measured by Alexander Dallas Bache on Dauphin Island in 1847. This granite marker is now in Ft. Gaines at the entrance to Mobile Bay. Although moved from its original location, it is the oldest known Coast Survey marker on the Gulf Coast."
More on this historic survey monument is here, in "Geodesy, by the US Coast and Geodetic Survey, Vol. 7" a free book available on the Google Play store: (
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"THE EASTERN OBLIQUE ARC
6. THE DAUPHIN ISLAND BASE LINE AND BASE NET, ALABAMA 1847
Location, measurement and resulting length of the Dauphin Island Base Line, Alabama, 1847.
When reckoner loitering for a primary baseline on the coast of Alabama and Mississippi in 1845, assistant F. H. Gerdes selected a site on Dauphin Island, and a preliminary measurement was made with a chain in 1845-1846. The measurement was made during May and June, 1847, by A. D. Bache, Superintendent of the Coast Survey. A full account of this measurement, and the only one published, will be found in Coast and Geodetic Survey Report for 1889, Appendix No. 17, pages 479-491, which permits of giving less space to it here than would otherwise be demanded.
This is the first baseline measured with the Bache-Wurdemann contact level compensating apparatus, 6 m in length, designed in 1845, and constructed at the survey office in 1845-1846. . . . "
In the Report of the Supertintendent of the US Coast & Geodetic Survey showing the progress of the work during the fiscal year ending with June, 1883, another free ebook available in the Google Play store, we find this: (
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"SECTION VIII
Alabama Mississippi Louisiana and Arkansas, including Gulf Coast, forts, and rivers
Reconnaissance for the connection of the Gulf Coast triangulation on Mobile Bay, Alabama, and vicinity with the primary triangulation at or near Atlanta Georgia. -- Having been charged with making a reconnaissance for triangulation between the Gulf of Mexico at or near Mobile Bay, and the primary triangulation near Atlanta, Georgia, assistant S. C. McCorkle proceeded to Mobile, Alabama, in January, 1883, and began a careful search to ascertain what points of the old triangulation could be found with which to connect the scheme of reconnaissance.
For transportation, which greatly facilitated his labors, Mr. McCorkle acknowledges his indebtedness to Capt. A. N. Damrell, United States Engineers, and to Capt. T. W. Lay, United States Revenue Marine.
In the explorations for the old strangulation marks on and near Mobile Bay, great changes of shoreline and other topographical features were found. The coast has been visited by gales of great severity since the former survey, and the shores of the Bay, especially at the points and bluffs where stations were generally established, have been washed away from 30 to 60 feet. Upon Dauphin Island, where search was made for the monuments marking the ends of the primary baseline measured in 1847, the granite blocks at East Base were found, but were lying on their sides apart from each other and entirely out of position. Search was made unsuccessfully for the underground marks. The blocks which had marked the West base could not be found. Nearly 2/3 of the island on the South side has been entirely submerged and the South Shore has been very largely washed away, while the North Shore line seems to have been greatly extended. Pelican Island has entirely disappeared."
It is clear from the NOAA website that this survey stone in the center of Fort Gaines is the historic baseline stone set by Superintendent Bache in 1847. It is also clear that this stone has been moved, so it no longer has any geodetic use, but is still a cool historic benchmarking and surveying thing to come see.