  We present a detailed description of the physical properties of our current
census of white dwarfs within 40 pc of the Sun, based on an exhaustive
spectroscopic survey of northern hemisphere candidates from the SUPERBLINK
proper motion database. Our method for selecting white dwarf candidates is
based on a combination of theoretical color-magnitude relations and reduced
proper motion diagrams. We reported in an earlier publication the discovery of
nearly 200 new white dwarfs, and we present here the discovery of an additional
133 new white dwarfs, among which we identify 96 DA, 3 DB, 24 DC, 3 DQ, and 7
DZ stars. We further identify 178 white dwarfs that lie within 40 pc of the
Sun, representing a 40% increase of the current census, which now includes 492
objects. We estimate the completeness of our survey at between 66 and 78%,
allowing for uncertainties in the distance estimates. We also perform a
homogeneous model atmosphere analysis of this 40 pc sample and find a large
fraction of massive white dwarfs, indicating that we are successfully
recovering the more massive, and less luminous objects often missed in other
surveys. We also show that the 40 pc sample is dominated by cool and old white
dwarfs, which populate the faint end of the luminosity function, although
trigonometric parallaxes will be needed to shape this part of the luminosity
function more accurately. Finally, we identify 4 probable members of the 20 pc
sample, 4 suspected double degenerate binaries, and we also report the
discovery of two new ZZ Ceti pulsators.
