  After decades of brown dwarf discovery and follow-up, we can now infer the
functional form of the mass distribution within 20 parsecs, which serves as a
constraint on star formation theory at the lowest masses. Unlike objects on the
main sequence that have a clear luminosity-to-mass correlation, brown dwarfs
lack a correlation between an observable parameter (luminosity, spectral type,
or color) and mass. A measurement of the brown dwarf mass function must
therefore be procured through proxy measurements and theoretical models. We
utilize various assumed forms of the mass function, together with a variety of
birthrate functions, low-mass cutoffs, and theoretical evolutionary models, to
build predicted forms of the effective temperature distribution. We then
determine the best fit of the observed effective temperature distribution to
these predictions, which in turn reveals the most likely mass function. We find
that a simple power law ($dN/dM \propto M^{-\alpha}$) with $\alpha \approx 0.5$
is optimal. Additionally, we conclude that the low-mass cutoff for star
formation is $\lesssim0.005M_{\odot}$. We corroborate the findings of Burgasser
(2004) which state that the birthrate has a far lesser impact than the mass
function on the form of the temperature distribution, but we note that our
alternate birthrates tend to favor slightly smaller values of $\alpha$ than the
constant birthrate. Our code for simulating these distributions is publicly
available. As another use case for this code, we present findings on the width
and location of the subdwarf temperature gap by simulating distributions of
very old (8-10 Gyr) brown dwarfs.
