Needing capital for his new venture, Rockefeller approached Flagler in 1867. Flagler's stepbrother Stephen Harkness invested $100,000 (equivalent to $ in ) on the condition that Flagler be made a partner. The Rockefeller, Andrews & Flagler partnership was formed with Flagler in control of Harkness' interest. The partnership eventually grew into the Standard Oil Corporation. It was Flagler's idea to use the rebate system to strengthen the firm's position against competitors and the transporting enterprises alike. Flagler was in a special position to make those deals due to his connections as a grain merchant. Equivalent to a 15% discount, they put Standard Oil in position to significantly undercut other oil refineries. By 1872, it led the American oil refining industry, producing . In 1877, Flagler and his family moved to New York City, which was becoming the center of commerce in the U.S.. In 1885, Standard Oil moved its corporate headquarters to New York City to the iconic 26 Broadway location.