  Stars are born with magnetic fields, but the distribution of their initial
field strengths remains uncertain. We combine observations with theoretical
models of magnetic field evolution to infer the initial distribution of
magnetic fields for AB stars in the mass range of 1.6 - 3.4 M$_{\odot}$. We
tested a variety of distributions with different shapes and found that a
distribution with a mean of $\sim$800 G and a full width of $\sim$600 G is most
consistent with the observed fraction of strongly magnetized stars as a
function of mass. Our most-favored distribution is a Gaussian with a mean of
$\mu$ = 770 G and standard deviation of $\sigma$ = 146 G. Independent
approaches to measure the typical field strength suggest values closer to 2 - 3
kG, a discrepancy that could suggest a mass-dependent and bimodal initial field
distribution, or an alternative theoretical picture for the origin of these
magnetic fields.
