Prior to the establishment of the United States Weather Bureau in the 1890's, volunteer civilian and military weather observers throughout the growing Nation observed and documented weather and climate data. Under NOAA's Climate Database Modernization Program (CDMP), which is managed through NOAA's National Climatic Data Center, these valuable data are being keyed into a digitized format, and their metadata collected. As part of this process, CDMP meteorologists closely inspect digital images of the original observers' forms – every image available, from every station to be keyed, over 200 to date. This means literally tens of thousands of these historic forms have already been inspected, one by one.

This keying project offers CDMP meteorologists the unique opportunity to see first-hand the observing practices of that day. It's probably not surprising that many of the weather elements observed in the 19th century are still recorded today, and that several elements have been added since then. But it's perhaps more surprising to note that these early observers at times took much more detailed observations than those in modern times, and recorded elements no longer observed, including vapor pressure, direction of cloud movement, and others, plus items now considered non-weather elements, such as water temperature and observations of auroras and solar halos.

In addition to differences in elements, close inspection of these early observers' forms has revealed other secrets. A few systematic errors have been uncovered, generally traceable to observing practices employed during certain time periods. Station moves which otherwise would certainly have gone undetected have been found. And occasionally, unusual items of historic significance find their way onto these weather forms, tidbits which reveal much about this period in our Nation's history, and which may be nearly as valuable in their own right as the observations themselves.