The overall rise in inequality in the USA since 1980 has been matched by a rise in inequality between places; local and regional development policies aimed at reversing this polarisation have seen limited success. We propose an explanation for the spatial polarisation of prosperity and the failure of the policies to remedy it. Our explanation is based on the interaction of monopoly power, agglomeration economies in technology clusters and the power of financial sector actors over non-financial firms—all phenomena characteristic of the post-1980 economy. We review evidence for each of these elements and propose some causal relationships between them, as an outline of an ongoing research programme.