  We present inelastic neutron scattering and magnetization measurements of the
antiferromagnetic insulator LaMnPO that are well described by a Heisenberg spin
model. These measurements are consistent with the presence of two-dimensional
magnetic correlations up to a temperature T$_{max}$ $\approx$ 700 K >> T$_{N}$
= 375 K, the N\'eel temperature. Optical transmission measurements show the T =
300 K direct charge gap $\Delta$ = 1 eV has decreased only marginally by 500 K
and suggest it decreases by only 10% at T$_{max}$. Density functional theory
and dynamical mean field theory calculations reproduce a direct charge gap in
paramagnetic LaMnPO only when a strong Hund's coupling J$_{H}$ = 0.9 eV is
included, as well as onsite Hubbard U = 8 eV. These results show the direct
charge gap in LaMnPO is rather insensitive to antiferromagnetic exchange
coupling and instead is a result of the local physics governed by U and
J$_{H}$.
