Elevation data is available from USGS as a Digital Elevation Model (DEM). This is obtained by digitizing contour lines on USGS topographical 1:250,000 scale maps. The data is set up as points on a grid covering a 1 degree quadrant with 90m resolution. 30m resolution data is being developed, but currently is only available for about half the US.
Data for New York state requires about 500 Mbytes, for the entire US it is about 10 Gbytes. This will increase 9-fold for 30m resolution data.
The US Defense Mapping Agency has 90m resolution data for the entire world, but it is classified. The only available world-wide data has 1km resolution, which is the same as is available for Mars!