Visitors walk the grounds of the Saugus Iron Works National Historic Site in Saugus, Mass. At right, a hammer sits among other tools in the blacksmith shop.

AP / WINSLOW TOWNSON

SAUGUS, Mass. — It ran for only 22 years, but the iron works established on the banks of the Saugus River in 1646 would free a colony from dependence on British manufacturing, create a model for the American factory town, and launch the world’s most powerful steel industry.

The Saugus Iron Works National Historic Site reopened to the public this spring after 18 months of construction to upgrade the facility, improve access, and restore the waterways so critical to its operation. The site celebrates the stories of the earliest Puritan inhabitants and the English iron workers and Scottish prisoners of war who helped lay the foundation for America’s iron and steel industry.

Most of the eight-acre site replicates the layout uncovered by archaeologists in the 1940s. Those digs revealed the remains of the blast furnace and mill buildings and structures, including remarkably preserved tailraces, water wheels, anvil bases, and thousands of artifacts.

Today the reconstructed site includes a blast furnace, forge, rolling and slitting mill (where large pieces of iron were rolled thin and cut into slivers to make nails), and a house. Seven waterwheels power equipment in the three main mill buildings; fires glow, giant bellows and gears clatter, and a 500-pound trip hammer strikes with deafening blows. In the museum, tools, equipment, and objects from the original iron works are displayed, along with artifacts indicating habitation of the site more than 10,000 years ago.

A short video takes visitors back to the pre-Revolutionary Massachusetts Bay Colony when Richard Leader recognized the ecological bonanza provided by the Saugus River in an area that was then Lynn. The river would provide water power and transportation; the local bogs and streams contained iron in the form of bog ore; and the region had thousands of acres of woodland needed to make charcoal to feed the blast furnace.

When the operation went bankrupt in 1668, the workers who had honed their skills there fanned out across the Colonies. “In a way,” said park ranger Curtis White, “it was the bankruptcy that spread the trade of iron and steelmaking. It forced talented workers to disperse across the young country, carrying their skills with them.”

One of the most striking aspects of the site is its marked levels of elevation, from the hilltop visitors’ center to the marshy riverbank. You can almost sense the movement of water through wooden millraces that powered the blast furnaces.

A switchback gravel trail offers easy access to the three main buildings for wheelchairs, baby carriages, or anyone who has difficulty with stairs. In addition, a large, raised model of the original iron works’ complex water system familiarizes sight-impaired visitors with the area’s topography.

Key to the success of the early iron works was the Saugus River, which bisects the park. Its waters supplied power to operate waterwheels, and small sailing vessels called shallops or lighters entered its “turning basin” to bring in raw materials or ship out iron products. The renovation restores open water to the area by removing invasive vegetation and improves biodiversity by enhancing native plant, fish, and wildlife habitat. Visitors can clearly recognize the pivotal role the river played in this historic enterprise.If you go

FROM PROVIDENCE: Take I-95 north to Massachusetts exit 43 (Walnut Street). Drive east toward Lynn and follow the brown National Park Service signs for 3.5 miles to the Iron Works at 244 Central St., Saugus.

VISITOR INFORMATION: Open daily 9 a.m.-5 p.m. through Oct. 31; closed Nov. 1-March 31. Free. Details at (781) 233-0050, or www.nps.gov/sair.