We study theoretically and numerically the ground state of a gas of 2D Abelian anyons in an external trapping potential. We treat anyon statistics in the magnetic gauge picture, perturbatively around the bosonic end. This leads to a mean-field energy functional, whose ground state displays vortex lattices similar to those found in rotating Bose-Einstein condensates. A crucial difference is, however, that the vortex density is proportional to the underlying matter density of the gas