Graphene, a two-dimensional material with a high mobility and a tunable conductivity, is uniquely suited for plasmonics. The frequency dispersion of plasmons in bulk graphene has been studied both theoretically and experimentally, whereas no theoretical models have been reported and tested against experiments for confined plasmon modes in graphene microstructures. In this paper, we present experimental measurements as well as analytical and computational models for such confined modes. We compare experimental measurements with theory for plasmon modes in interacting arrays of graphene strips and demonstrate a good agreement. The comparison between experimental and theoretical results reveals the important role played by interaction among the plasmon modes of neighboring graphene structures.