 Over the course of 20 years Fisher developed a detailed map of the Delaware Bay with help from his brother-in-law, Samuel Rowland, and teacher Thomas Godfrey.The chart was very accurate for the day, showing observations of the exact latitude and longitude, and soundings, information about harbors, stream inlets, shoals, and ship channels.The chart was engraved by James Turner, funded by a group of local merchants and ship owners, and printed in 1756 in Philadelphia by printer John Davis.