  Opposite spin Landau levels in a quantum well can be brought into coincidence
by tilting the magnetic field away from normal orientation. We demonstrate that
the magnetotransport anomaly at integer filling factors that was recently
discovered by Pan {\it et al} is due to such a coincidence. By performing exact
diagonalization calculations using microscopically evaluated effective
electron-electron interactions, we are able to establish that the electronic
ground state at coincidence is an Ising quantum Hall ferromagnet and that the
low energy excitations correspond to the formation of a domain wall.
