  We present a new sample of M subdwarfs compiled from the 7th data release of
the Sloan Digital Sky Survey. With 3517 new subdwarfs, this new sample
significantly increases the number of spectroscopically confirmed low-mass
subdwarfs. This catalog also includes 905 extreme and 534 ultra sudwarfs. We
present the entire catalog including observed and derived quantities, and
template spectra created from co-added subdwarf spectra. We show color-color
and reduced proper motion diagrams of the three metallicity classes, which are
shown to separate from the disk dwarf population. The extreme and ultra
subdwarfs are seen at larger values of reduced proper motion as expected for
more dynamically heated populations. We determine 3D kinematics for all of the
stars with proper motions. The color-magnitude diagrams show a clear separation
of the three metallicity classes with the ultra and extreme subdwarfs being
significantly closer to the main sequence than the ordinary subdwarfs. All
subdwarfs lie below (fainter) and to the left (bluer) of the main sequence.
Based on the average $(U,V,W)$ velocities and their dispersions, the extreme
and ultra subdwarfs likely belong to the Galactic halo, while the ordinary
subdwarfs are likely part of the old Galactic (or thick) disk. An extensive
activity analysis of subdwarfs is performed using H$\alpha$ emission and 208
active subdwarfs are found. We show that while the activity fraction of
subdwarfs rises with spectral class and levels off at the latest spectral
classes, consistent with the behavior of M dwarfs, the extreme and ultra
subdwarfs are basically flat.
