  We have measured the hyperfine splitting of the $7P_{1/2}$ state at the 100
ppm level in Fr isotopes ($^{206g,206m, 207, 209, 213, 221}$Fr) near the closed
neutron shell ($N$ = 126 in $^{213}$Fr). The measurements in five isotopes and
a nuclear isomeric state of francium, combined with previous determinations of
the $7S_{1/2}$ splittings, reveal the spatial distribution of the nuclear
magnetization, i.e. the Bohr-Weisskopf effect. We compare our results with a
simple shell model consisting of unpaired single valence nucleons orbiting a
spherical nucleus, and find good agreement over a range of neutron-deficient
isotopes ($^{207-213}$Fr). Also, we find near-constant proton anomalies for
several even-$ N$ isotopes. This identifies a set of Fr isotopes whose nuclear
structure can be understood well enough for the extraction of weak interaction
parameters from parity non-conservation studies.
