No. 7532 Advertisement in Dorchester and Quincy Directory, 1868-9, from A. Plson, dealer in fish of all kinds, Field’s Corner.
The Boston Directory for 1870 has an entry for Alexander Polson, fishmarket, Park cor. Exchange, h. South, wd 16 [Dorchester]. Exchange Street was located about where Mapes Street is today, leading south from Park Street along the railroad tracks (now MBTA tracks).