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 1860 and 1870 census publications. These data, which came from sources outside the Census Office (predecessor of the Census Bureau), show only the land area of the States and territories.

The first comprehensive area measurement information was published as part of the 1880 census. The measurements were done for many more types of geographic entities than in previous censuses. There were separate land and water area figures for the Nation, the individual States and territories, and for the first time, counties. Also, the Census Office began to calculate its own area measurement values. A special publication described the measurement techniques, sources consulted, and maps used. From 1890 through 1930 there were gradual improvements in the quality and scope of the area measurement presentations, as the Census Bureau began to provide area measurement information for geographic entities below the State and county level, such as for more populous incorporated places and minor civil divisions (MCDs).

There were important new advances in conjunction with the 1940 census. For the first time, the Census Bureau provided area measurement information for every MCD regardless of its population, and every incorporated place with a population of 1,000 or more. The Census Bureau used aeronautical charts from the U.S. Coast and Geodetic Survey (scale of 1:500,000) to derive the total area of the United States and of each State; for counties, it used the U.S. Geological Survey’s (USGS) State topographic quadrangle maps (also at a scale of 1:500,000); for county subdivisions and places, it used county highway maps. It then adjusted the State totals to agree with the previously derived U.S. total, and the county totals to agree with the State totals.

The Census Bureau defined land to include all dry land, land temporarily or partially covered by water (except tidal flats), and islands more than 40 acres in size. It defined inland water as permanent streams, sloughs, estuaries, and canals except those less than one-eighth of a mile (660 feet) in width, and permanent lakes, ponds, and reservoirs except those of less than 40 acres. Notes and References 15-2Area Measurement/Water Classification