POI file for High resolution GPS Markers?

I think what you are talking about are called benchmarks at http://www.geocaching.com/
where benchmarks are listed.

... and geocaching can be a lot of family fun.

The text from geocaching.com says:

What is a benchmark?
A benchmark is a point whose position is known to a high degree of accuracy and is normally marked in some way. The marker is often a metal disk made for this purpose, but it can also be a church spire, a radio tower, a mark chiseled into stone, or a metal rod driven into the ground. Over two centuries or so, many other objects of greater or lesser permanence have been used. Benchmarks can be found at various locations all over the United States. They are used by land surveyors, builders and engineers, map makers, and other professionals who need an accurate answer to the question, "Where?" Many of these markers are part of the geodetic control network (technically known as the National Spatial Reference System, or NSRS) created and maintained by NOAA's National Geodetic Survey (NGS).

Thanks WalkThisWay, I couldn't remember what it was called, it's the Spatial Reference System.

In the US almost all surveying west of the 13 original States starts from one of 37 Principal Meridians.

Check them out at www.pmproject.org

Shanks