  We present the first phenomenological study of the masses of orbitally
excited baryons in large N_c QCD. Restricting here to the nonstrange sector of
the L=1 baryons, the 1/N_c expansion is used to order and select a basis of
effective operators that spans the nine observables (seven masses and two
mixing angles). Fits are performed using subsets of the complete set of nine
operators, including corrections up to O(1/N_c) where leading order is N_c^1.
This study shows that the 1/N_c expansion provides an excellent framework for
analyzing the mass spectrum, and uncovers a new hierarchy of operator
contributions.
