Pickman was instrumental in the commercial development of much of the heart of historic Salem. In 1815 he and John Derby III acquired property belonging to Derby family heirs to develop Derby Square, which would encompass three brick commercial rows. The Pickman-Derby Block, built in 1817, still stands.
Pickman was instrumental in shaping Salem's commercial landscape. He partnered with John Derby III to acquire land from the Derby family in 1815 and went on to develop Derby Square, a three-row brick complex that still stands today. The Pickman-Derby Block, built in 1817, is a testament to their collaboration.