Gustave Bergquist began building pianos in New York City as early as 1843, with his factory located at 115 Franklin Street. From 1846 â 1850, Bergquist was in partnership with Peter Wennerstrom, building instruments under the name of Wennerstrom & Bergquist. After the partnership ended in 1850, Bergquist continued to build pianos on a very small scale until just before 1880. Instruments by Bergquist were handmade, top quality instruments and they are exceedingly rare today. Any instruments by this firm are now considered to be of museum caliber.