Love wave phase velocity maps provide essential constraints on radial
anisotropy and deformation in the crust and upper mantle. However, the
phenomenon of overtone interference causes scatter and systematic bias
in the velocity measurements and impedes efforts to image small-scale
anisotropic variations. We develop an approach for identifying Love wave
measurements that are biased by overtone interference, demonstrate its
efficacy with EarthScope USArray data, and determine the first
earthquake-derived Love wave phase velocity maps for the entire
conterminous U.S. in the period range 35-75 s. We show that radial
anisotropy in parts of the crust and most of the lithospheric mantle is
necessary to reconcile these maps with Rayleigh wave phase velocities.
Our results convey the impact and geographic variability of overtone
interference, offer an easy-to-implement method to ameliorate this
impact, and present high-resolution constraints on radial anisotropy
beneath North America.