Abstract | A simplified mechanical model is developed for heritage masonry buildings to address the problem of the collective seismic vulnerability of historical cities. Our focus is the derivation of capacity curves based on parameterized first-mode structural models that are flexible enough to represent an ensemble of similar buildings. The structural model estimates lateral strength using a Mohr-Coulomb type failure criterion of the load-bearing walls deforming in-plane in shear in combination with a yield-line mechanism for the out-of-plane flexural deformation of the orthogonal walls. The resulting equivalent models are simple enough to allow an analytic first-mode representation of their seismic behavior that is suitable for evaluation via static pushover in a manner that is consistent with current performance-based seismic assessment frameworks.