This quarry was located on Crotch Island in the southeastern part at Thurlow Head. The operator was the Crotch Island Granite Co. of Grand Central Terminal in New York. The granite from the quarry, referred to as "Crotch Island," was reportedly a lavender-tinted medium-gray color with a coarse texture. "Its polished surface is attractive on account of the contrasts between pale lavender, white, and black particles, and it is therefore in demand for base courses and wainscoting."

The Ryan-Parker Quarry opened about 1880. When the quarry was measured in 1905 it was about 700 by 300 feet and had a depth from 20 to 75 feet with an average of 35 feet. Transport of the granite was by gravity on tracks 75 to 100 feet long to the wharves. At the time of the report the quarry had been idle since 1916.