The company appointed Thomson as chief engineer at a salary of $5000 a year. Thomson did a brilliant job. With unbounded energy he sought out the best routes, making allowances for grades and river crossings. With Herman Haupt, he co-designed what became famous as "Horseshoe Curve" and built a railroad with practicable grades. He switched the fuel from wood to coal for the locomotives; other lines followed suit, thus opening up a new demand for coal, which the PRR shipped to all railroads. The through line between Philadelphia and Pittsburgh opened for traffic in February 1854, and made Philadelphia a major outlet for long-haul traffic from the west. This connection also strengthened its port, which had access to the Atlantic Ocean.