USGS National Elevation Dataset 1/3 arc-second (USGS/NED)

The National Elevation Dataset (NED) used to be* the
primary elevation data product of the USGS. The NED is a seamless
dataset with the best available raster elevation data of the
coterminous United States, parts of Alaska, Hawaii, and some
territorial islands. The NED is derived from diverse source data
that are processed to a common coordinate system and unit of
vertical measure. NED data are distributed in conformance with
the North American Datum of 1983 (NAD 83). All elevation values
are in meters and, over the conterminous United States, are referenced
to the North American Vertical Datum of 1988 (NAVD 88). The vertical
reference will vary in other areas.

*For over 15 years, the NED was the primary elevation data product
of the USGS’ National Map. However, it has been renamed and now
considered just one component of elevation in The National
Map after the 3D Elevation Program became operational.