If the people in the Army Corps of Engineers who built Dunlap's Creek Bridge in Brownsville back in 1839 could see it now, they would not believe their eyes. The nation's very first cast iron, metal arch bridge built for horse and buggy traffic is still around, now with all kinds of vehicle traffic.

"Never meant for the weight of today's cars and trucks, the bridge is still in very good shape," said Marc Henshaw, who will be the featured guest speaker at the bridge's 170th birthday celebration from noon to 3 p.m. on Saturday. "PennDOT comes in every few years to give it a new coat of paint, but the bridge that heralded the coming of age of the United States into the industrial age is still holding up quite well."

Built over a three-year time period, the history-making bridge cost $40,000 to complete using 140 tons of iron shipped from Portsmouth, Ohio, to the Vulcan Iron and Machine Works in Brownsville.

Designed by Corps Captain Richard Delafield, who graduated from the U.S. Military Academy at West Point with a focus on engineering, the bridge was constructed under the management of Brownsville residents John Snowden and James Herbertson. The latter created the patterns for the cut pieces and later established a foundry of his own in Brownsville on the site of present-day Fiddle's Restaurant.

"Brownsville was probably chosen as the site of the nation's first cast iron bridge because it lies along the National Road, was a point of departure for settlers moving West and had a powerful merchant class at the time," Mr. Henshaw said.

Although the bridge's birthday celebration is slated for the Fourth of July, the guest speaker said he never came across any information that identified the specific day the bridge officially opened.

"We do know that construction was completed in 1839 and probably in the summer," he said.

Crossing Dunlap's Creek with an 80-foot span along Brownsville's main thoroughfare, the bridge replaced an earlier small, chain suspension bridge built in 1808 by Judge James Finley of Brownsville, considered by some historians the father of the modern suspension bridge.

In 1820, Finley's bridge collapsed under the weight of snow and a six-horse wagon team and was replaced by the current Dunlap's Creek Bridge, now listed on the National Register of Historic Places and designated a National Historic Civil Engineering Landmark.

Although the world's first cast iron bridge was built in Coalbrookdale, England in 1780, Mr. Henshaw said the Dunlap's Creek Bridge "represents an achievement of the fledgling industrialization and technological innovation of the early United States."

"Interestingly, the Vulcan Iron and Machine Works never built another bridge after the one that spans Dunlap's Creek, probably because the enterprise went into the more lucrative manufacture of steam engines and boilers for steam boats," he said.

During the bridge's 170th birthday celebration, a number of elected federal, state and local officials will speak along with Mr. Henshaw. The festivities will also include music, a cake cutting ceremony, food and craft vendors.

"Because of the historical significance, we'll also display photos of Brownsville taken at different eras along with architectural prints of the bridge," said Tracy Zivkovich, chairwoman of the celebration committee. "The bridge has also been targeted as a tourist destination as part of the Dunlap's Creek restoration project, which plans to develop the space around the bridge and creek as a public green space."

The Brownsville Area Revitalization Corp. is sponsoring the event.

Paula Johnston, event publicist, said she feels that the prouder someone is of their community, the more likely he or she would be to develop and take care of it.

"Part of our goal is to make people aware of their cultural and historic riches," she said. "I'd love to see people come out, look at the bridge, enjoy the speakers and help us celebrate."

For more information, call 724-785-9331.