Heh, looking at my neighborhood, the smallest available file is a scan of the 1933 7.5-minute Sierra Madre quad, 5.24MB, and the largest is the 1979 30x60 minut

Heh, looking at my neighborhood, the smallest available file is a scan of the 1933 7.5-minute Sierra Madre quad, 5.24MB, and the largest is the 1979 30x60 minute Los Angeles quad, 44.53MB. Most of the 7.5 minute quads seem to be in the 15-30MB range. So I don't feel so bad about my "shakey" estimate of individual map sizes!