In recent times, Massachusetts has surprised many commentators by its ability to continuously reinvent itself as a successful regional economy. In this paper, we seek to penetrate the region's surprising resilience and better understand regional specialization, growth, and decline. We deploy a historical database of high-tech companies designed to conduct regional technology mapping exercises. We seek to advance both theoretical and empirical knowledge of regional competitive advantage along with a related set of concepts. These concepts include Marshallian externalities, regional technological capabilities, "self-sustaining clusters," and regional innovation systems. We previously presented results from an empirical investigation of "self-sustaining" technology "mini-clusters" in a sub-region of Massachusetts. Here we interrogate the database using a set of regional competitive advantage indicators and extend our focus to the State of Massachusetts and, for comparison purposes, California's Silicon Valley.