Dillsburg, PA. (Dec 1st, 2010) – "Some things are just built to Last": 

Ever heard of the Rockville Bridge?
Joseph Machine Company is located approximately 25 minutes due south of Marysville PA, the home of a historical structure. At least one employee at JMC passes this amazing structure on his way into work every weekday. I myself have passed it and not realized the significance it holds in the world of railroad bridges.  It turns out that it is actually the longest arched stone masonry (composite) bridge in the WORLD, built in the early 1900's.  Here is what the www.explorePAhistory.com has to say about this magnificent bridge that was BUILT TO LAST.

Rockville Bridge
Region: Hershey/Gettysburg/Dutch Country Region
County: Perry
Marker Location:US 11 and 15 at N end of Marysville

Historic Marker Text -
The longest stone masonry arch railroad bridge in the world, one mile to the south, was built 1900-02. With forty-eight arches, it has a length of 3,820 feet. This was the third bridge constructed here by the Pennsylvania Railroad. A wooden structure had been built 1847-49, followed by an iron bridge in 1877.

"At Rockville, just above the capital city, they have thrown across the Susquehanna a four-track bridge of monolithic stone seven-eighths of a mile long and stepped in graceful arches as enduring as the mountains that look down on the beautiful river. . . . it has been built to last forever."
- Writer and novelist Frank H. Spearman, The Strategy of Great Railroads, 1904.

Old Rockville Bridge, circa 1892
Credit: Courtesy of the Railroad Museum of Pennsylvania, Operated by the Pennsylvania Historical and Museum Commission

Rockville Bridge, an icon of railroad engineering, is the crowning achievement of William Henry Brown, chief engineer of the Pennsylvania Railroad. And this amazing stone bridge, composed of 220,000 tons of stone that took 800 workers two years to build, also stands as a monument to overcoming frustration. As the United States matured into an industrialized nation after the Civil War, the trains that moved the nation forward grew longer, heavier, faster, and more frequent. Wooden bridges that were perfectly adequate in the 1840s quickly began to wear out. Some even went up in smoke from sparks spewed from the stacks of passing steam locomotives. And with the growth of business, PRR's main line no longer carried a mere seven trains a day but as many as 100.

Though iron was stronger than wood, spectacular and often tragic failures on some railroads showed what could happen when iron spans were overloaded and under-maintained. As a result, Brown soon began pushing the idea that only costly stone-arch bridges -like those used in the earliest days of railroading - were durable enough to withstand both the passage of time and the growing number of mainline freight and passenger trains. Beginning in 1888, he decreed that replacement bridges on PRR's busiest routes, including its Philadelphia-Pittsburgh main line, would reflect a revival of stone-arch technology. Under Brown's hand, contractors installed mainline stone-arch bridges at the rate of two or three a year, in sizes and varieties that ranged from a single arch to the majestic forty-eight-arch Rockville Bridge near Harrisburg.

Rockville Bridge Old & New
Credit: Courtesy of the Railroad Museum of Pennsylvania, Operated by the Pennsylvania Historical and Museum Commission

The Rockville Bridge required the expertise of as many as 300 stonemasons, Italian immigrants or Italians who relocated from Curwensville in Clearfield County, site of some of Pennsylvania's largest quarries and source of much of the sandstone used in the bridge. Each of the forty-eight arches measured seventy feet long, and the four arches at each end gently curved to accommodate the swing of the tracks as they turned to parallel the river.

Today, many people call Rockville Bridge "the longest stone-arch bridge in the world," but that's only partly true—only the visible outer layer of its form is stone. The piers and spandrels (the area between the arches) are filled with concrete, making it technically a composite structure. In all, the bridge required not only 220,000 tons of stone but an estimated 600,000 barrels of cement. Measuring 3,820 feet long, it carries four tracks at an elevation fifty-two feet above the river's low-water mark. The price tag was $975,150. The bridge opened on March 30, 1902. Less than three months later, the railroad inaugurated the most famous regularly scheduled passenger train to use the structure: the overnight New York-Chicago Pennsylvania Special, which later became the Broadway Limited.

Rockville Bridge
Courtesy of Dan Cupper

Because the bridge was considered to be a military target, armed guards protected it during World Wars I and II. It got a boost of publicity in 1925 and 1926, and again in 1950, when PRR featured it on its widely known wall calendar series. The bridge withstood the flood of March 1936 and an even heavier assault from Tropical Storm Agnes in June 1972. By contrast, the 28-arch stone Shocks Mill Bridge, built thirty miles downstream by one of the two contractors who built Rockville, washed out in the Agnes flood.

In 1968, ownership of Rockville Bridge changed to Penn Central when PRR merged with the former New York Central Railroad. Penn Central went into bankruptcy in 1970, and became part of the government-backed rescue plan called Conrail in 1976. Conrail brought the railroad into the black, returning it to private investors in 1987.

Shortly after the PRR opened its now famous 4-track stone bridge in 1902, it demolished the double track iron bridge it had used since 1877
Credit: Courtesy of the Railroad Museum of Pennsylvania
On August 19, 1997, the accumulated effect of repeated freeze-thaw cycles forced some of the bridge's stones out of alignment at Pier 19 (the nineteenth pier from the east shore). When a heavy coal train passed over the weakened spot, the south spandrel wall failed, sending tons of stone, rails, ties, and four 100-ton loaded hopper cars into the Susquehanna. The repair and cleanup cost about $1 million, approximately the original price of the entire bridge. Since then, crews have strengthened the structure with steel tie-rods and braces, a process that continued under the ownership of Norfolk Southern Corporation, which added this portion of Conrail to its system on June 1, 1999.

To the very end of the Pennsylvania Railroad's corporate existence, Rockville Bridge remained the largest of the company's 10,107 bridges. Though PRR built other large stone-arch bridges after Rockville, within a few years the construction industry had perfected the technology of reinforced concrete. Still later, pre-cast concrete sections and welded steel girders came into favor. As a result, the art and craft of the stone mason's skill fell into disuse, but remains spectacularly showcased at Rockville.

Dan Cupper, Rockville Bridge: Rails Across the Susquehanna (Halifax, PA: Withers Publishing, 2002).
Ed. Morgan, The Quarries of Curwenville: the People, the Legacy (NP, ND).
Henry O. Tyrell, History of Bridge Engineering (Chicago: 1911).
William Shank, Historic Bridges of Pennsylvania (York, PA: American Canal and Transportation Center, 1974).