Allyson-- The survey marker is placed by the Coast and Geodetic Survey. They maintain a network of these throughout the country to aid in surveying. Some are fairly involved groups of related markers, others like this one are probably individual marks useful for local surveying. Despite being shown on the topo map, I can't find this one in the current database of "published" marks, so it may not be considered trustworthy.
It was quite a sight looking down to the bridge and the valley below it...very scenic.
correction to original post "above *sea level"
This is actually my family's property, I grew up on the land. My family (Hodapp's) still own the property. I remember the day the bridge was closed. I was very young maybe 6, which would be the early 90s. There are two houses that sit close to the bridge both with the name Hodapp, that is where the Hodapp Bridge name generated. I am curious if you know if the plaque on the bridge from the US Geolocigical Survey means anything specific or if it just states the above see level facts?
A few years ago I stopped and talked to a woman at the house east of the bridge . She told me the bridge was always referred to as Hodapp Bridge named after the Hodapp family that lived in the house as seen in picture #3 for "many, many years". I believe the bridge has been closed for aprox. 15 to 20 years since the 90's.