There were a smattering of craft breweries during that gap, they just had relatively small distribution compared to the Big Boys. Anchor Brewing has been going since pre-prohibition, for instance. But no one outside the Bay Area sought it out until the 60s, I believe. New Albion brewing, Bridgeport brewing (not the original name), Boston Beer Company, Bell's Brewing, Blitz-Weinhard...those are just the ones I remember off the top of my head