The Horseshoe Curve route from Altoona to Johnstown in Pennsylvania is named for its most prominent feature, the tight 220-degree turn that has made it possible for trains to cross the Allegheny Mountain Range since 1854. From its opening day, Horseshoe Curve was an engineering marvel, a tourist and railfan attraction, and a strategic artery for rail transport from the American East Coast to the Midwest. More than 150 years after its construction, and 40 years after becoming a U.S. National Historic Landmark, the route remains one of the busiest stretches of track in the world.

This famously scenic route starts 10 miles (16 km) east of Horseshoe Curve, in the Altoona freight yards. From Altoona, the tracks climb steadily westward to the Curve and then continue up to the three Gallitzin Tunnels at the 2,200-foot (670 m) summit of the Alleghenies, where they pass under the old town of Tunnel Hill. Beyond the summit, the route passes Cresson and then descends steadily for about 30 miles (48 km) past branch coal lines, through woodlands and small towns, to Johnstown. The route is interesting and at times challenging, with its many curves and changes in elevation. One if its most striking features is that engine crews who have rounded the Curve can watch the rest of their train moving in the opposite direction.

A Norfolk Southern locomotive passes the iconic stone shed at Horseshoe Curve. Research trip photo.

Here's an aerial view of the Curve, taken from maps.live.com. (Click to go to the live maps site, where you can zoom in to better see the long freight train rounding the Curve.)

Until the completion of Horseshoe Curve, there was no continuous rail line through the Alleghenies between the trading centers of Philadelphia and Pittsburgh. The chief obstacle was grade. A workable route required a grade of no more than two percent—a change in elevation of two feet for every 100 feet of track. No locomotive power then available could get a train up a steeper grade, nor could any braking system of the day keep a train from running out of control on the downgrade. But the gentlest grade anyone could envision over the mountains was an impossible six to eight percent.

In the late 1840s, J. Edgar Thomson, visionary chief engineer (and later president) of the Pennsylvania Railroad (PRR), hit upon an ingenious solution. He proposed running the right-of-way up one side of a valley and then routing the track back on itself in a hairpin turn up the other side. It more than doubled the length of the track but reduced the grade to a manageable 1.8 percent. Work began in 1851. Over the next three years, several hundred mostly Irish immigrants built the entire loop and completed the route, using only pickaxes, shovels, and gunpowder. By the end of 1854 the route from Altoona to Conemaugh was double-tracked.

Traffic steadily increased around Horseshoe Curve. By 1900, the Pennsylvania Railroad had added a third and fourth track, and dozens of trains were rumbling around the Curve every day. Those trains became longer and heavier as diesel-electric locomotives supplanted steam. The 1950s and 1960s saw maintenance on Horseshoe Curve suffer along with the railroad’s fortunes, as railroads lost business to air and road freight services. By 1976, when the Consolidated Rail Corporation (Conrail) took over the old PRR lines, the route’s condition had deteriorated. Worn rails, wobbly ties, and other consequences of neglect took years to correct. As part of the refurbishment, Conrail removed line number 2 from the Curve in 1981, reducing the number of tracks to three. That was—and still is—enough to handle the traffic, given the power of modern locomotives.

You can see the "ghost" of the 4th track in this photo taken near the Curve.

By the time Norfolk Southern Railway took over Conrail's Pennsylvania lines in 1999, the 40 miles of line from Altoona to Johnstown were fully restored. Today the valley resounds with the roar of diesel-electric engines and the whine of dynamic brakes. And railfans from many countries still come in droves to gather and watch the trains negotiate Horseshoe Curve, the United States’ unofficial railroad shrine.

The Visitors Center at Horseshoe Curve National Historic Landmark. Research trip photo.

In Train Simulator 2, the Horseshoe Curve route will be modeled in high detail, from Altoona to Johnstown.

Click here to see some of the high-detail scenery models for this route.

Click here to see renders of the locomotives and rolling stock for this route.