Along Elliott Way near the Yacht Club, red bricks scatter among the shoreline rocks—remnants of the William A. Underhill Brickyard that operated on Croton Point's northern end. These "Croton Point bricks" carried maker's marks; some featured Underhill's initials (WAU), while others bore the stamp "IXL," a marketing claim meaning "I excel" at brickmaking. During the 1850s brickmaking boom, over 25…