The magnetic domain structures formed at grain boundaries in recrystallized iron foils have been analyzed using Lorentz electron microscopy. Five basic types of domain structures have been observed at grain boundaries in iron: (1) Domain walls which penetrate through the boundary indicating ``no interaction,'' (2) double spike reverse domains, (3) single spike reverse domains, (4) echelon domains, and (5) domains of closure. Attempts to correlate the stability of the various domain types with the magnetic pole density of the grain boundary led to the following conclusions: (a) Double spike and ``no interaction'' domains appear to be associated with low pole densities while domains of closure appear to be associated with relatively larger pole densities and (b) no clear statement can be made with respect to the relative stabilities of the single spike and echelon domains due to difficulties in determining the magnetization direction within the domains and within the grain itself. They appear to overlap the pole densities of the other structures and each other as well. It is suggested that grain boundaries are important sources of reverse domain nucleation in polycrystalline ferromagnetic materials. The results emphasize the importance of the internal magnetostatic energy in determining the magnetic domain structure of iron.