HARTFORD — Final congressional approval came Friday for the creation of a Coltsville National Historical Park dedicated to the accomplishments of Samuel Colt and the role that his firearms and factory played in the Industrial Revolution.

Plans for the new national historical park include a 10,000-square-foot visitor center in the old Colt factory under the iconic blue onion dome in Hartford. An elevator and observation platform would give visitors a view of the factory floors below and allow people to visit the dome itself. It's unclear how soon the historical park might open.

"Today marks the culmination of more than a decade of work to preserve the legacy of American innovation and manufacturing that is Coltsville," said U.S. Rep. John Larson, D-1st District, who led the effort to create a national historical park in Hartford. "There is still work left to see this designation come to fruition, and I look forward to working with the National Park Service."

Funding for Coltsville was contained in a $577 billion defense bill approved Friday by the U.S. Senate. The legislation had already cleared the House of Representatives.

Larson and Connecticut's two U.S. senators, Richard Blumenthal and Chris Murphy, said they would work to ensure that the National Park Service budget contains money for the Coltsville project. Larson said that federal, state and local officials will also need to work together to provide a detailed plan for the park.

"Everybody's on the same page, everybody's pulling in the same direction," said Larson, who was attending a celebratory party Friday at Coltsville.

In response to questions about the possibility that it might take years for the park to open, Larson said he doesn't know what the timetable will be, but that efforts would "begin immediately" to make it happen as soon as possible.

Hartford Mayor Pedro Segarra also applauded the federal approval, noting that the city has already contributed more than $7 million for Coltsville improvements, including $5 million in state bond funds for additional residential units in the South Armory building and $2 million for streetscape work.

By some estimates, the planned park could eventually draw 200,000 visitors a year, but one Connecticut historian said it is likely to take years for Coltsville to achieve that sort of popularity.

The space for the visitor center would be provided in Colt's East Armory by its developers, CG Management, and the project's largest investor, Chevron TCI, an arm of the oil giant, according to CG's owner, Lawrence Dooley.

In March, the Congressional Budget Office estimated that creation of a 260-acre Coltsville National Park would cost taxpayers about $9 million over five years for planning, building restoration and landscaping. The area was designated as a national historic landmark in 2008 and advocates have been lobbying hard to win national park status.

"This will be a great step for Connecticut and for Hartford," said Blumenthal, praising the efforts of the state's congressional delegation. He said that Larson "deserves the lion's share of the credit."

Blumenthal said that a Coltsville National Historical Park "will drive economic growth … for Hartford and Connecticut" through a combination of tourism, housing development and commerce.

Murphy called congressional approval of the park "a dream come true for Connecticut."

A major difference between a national park such as Yosemite or Acadia, and national historical parks like the one in Lowell, Mass., or what's planned for Coltsville, has to do with size. Most national parks tend to be tens of thousands of acres of open space, while historical parks are normally far smaller and dedicated to a specific theme.

Hopes for the Coltsville park go far beyond the East Armory factory building where Colt created his landmark revolver, the "gun that won the West," and a manufacturing system that changed American industry.

The proposed park is also expected to include Hartford's Colt Park, as well as the residence of Samuel and Elizabeth Colt, called Armsmear, and the Church of the Good Shepherd and neighboring gardens. Many of the buildings that would become part of the national park are now in private hands.

Hartford officials say the goal is to transform the area around Coltsville and Colt Park. There are schools next to Colt Park, but also sections of rundown housing, bland industrial buildings and streets with a reputation for drugs and prostitution, a reputation that Coltsville supporters believe can be changed.

"It would create a neighborhood where people can come and recognize … the character and historical significance of Colt and Hartford," said Thomas Deller, the city's director of development services.

"Think of Lowell, Mass.," Deller said, citing the national historical park in that city that preserves the textile mills that made Lowell a center of manufacturing in the 19th and early 20th centuries. Deller said that the eventual site of the Lowell national park started out as nothing more than "a bunch of rundown, underutilized mills," but is now a thriving tourist and education center.

"In many ways, what we're trying to achieve at Coltsville is the same sort of thing," Deller said.

Richard Malley, head of research and collections for the Connecticut Historical Society, called the proposed Coltsville National Park "a long-term project. … It won't happen overnight." Malley said the park in Lowell "took years and years to get to the point where it was recognized as a model for interpreting industrial and cultural history."

Malley said he believes that the Coltsville project can tell "an important story" about "the impact of the Industrial Revolution in Connecticut and elsewhere. ... I think it can symbolize the whole process of innovation in the 19th and 20th centuries."

Friday's U.S. Senate vote was the culmination of years of lobbying by Connecticut's congressional delegation, state and local officials and historians.

In a 2009 federal study on the feasibility of creating a Coltsville national park, the researchers noted that the Museum of Connecticut History and Wadsworth Atheneum Museum of Art "have collections of Colt firearms, machinery and memorabilia related to Samuel and Elizabeth Colt and Colt Firearms Company."

"Both museums have indicated an interest in participating in a collaborative effort to interpret Coltsville in partnership with the National Park Service," the report noted.

Malley said that the Museum of Connecticut History has the most important Colt firearms collection in existence.

According to the study, creating a Coltsville National Historical Park would offer a "unique opportunity" to offer visitors a learning experience about firearms manufacturing and the roles of Samuel and Elizabeth Colt in transforming American industry.

Such a museum would also provide educational experiences about the precision technology developed by Colt and its impact on everything from the making of sewing machines to automobiles. The park would also emphasize the importance of Samuel Colt as an entrepreneur and his skill in marketing his products, as well as showing "life on an urban industrial community," the authors of the report concluded.

"We're very excited," said Dooley, owner of the managing partner of the Coltsville development project. He said it now appears that this historical section of Hartford "is getting the recognition it absolutely deserves."

Chevron TCI (which stands for tax credit investor) has "committed significant resources, not only in tax credit investments but in equity investments," Dooley said.