Since all locomotives of the time were steam-powered, many railroads had favored coal as their engines' fuel source after wood-burning models were found unsatisfactory. The L&N guaranteed not only its own fuel sources but a steady revenue stream by pushing its lines into the difficult but coal-rich terrain of eastern Kentucky, and also well into northern Alabama. There the small town of Birmingham had recently been founded amidst undeveloped deposits of coal, iron ore and limestone, the basic ingredients of steel production. The arrival of L&N transport and investment capital helped create a great industrial city and the South's first postwar urban success story. The railroad's access to good coal enabled it to claim for a few years starting in 1940 the nation's longest unrefuelled run, about from Louisville to Montgomery, Alabama.