We study how bankers' expertise in identifying productive projects impacts the economic structure. We examine the U.S. 1980s interstate banking deregulation as a quasi-natural experiment on the structural transformation of non-financial sectors across states. The economic structure of those states with deregulated banking sectors became closer to each other because bankers brought their expertise to find productive projects across state borders. We build a two-state, two-sector search-and-matching model where bankers' expertise determines sector-specific matching efficiency between bankers and producers. As deregulation makes bankers' expertise more accessible across states, the economic structure converges across states, especially when firms depend on external funding. Outputs are concave in the level of bank penetration. The relationship between output and bank penetration is concave: moderate levels of penetration reduce credit misallocation and boost output, but excessive penetration results in inefficiencies as guest banks crowd out local banks, diverting resources from more productive sectors.