Returning a stream to its Civil War-era condition will represent the first construction step in a $95 million project to send the Gettysburg battlefield back in time.

The stream is part of a much wider effort to undo changes to geographic features made over the 142 years since the battle and to build a new visitor center and museum, designed to evoke a Pennsylvania farm complex.

A ceremony Thursday marked the start of work on Guinn Run, a waterway that was dammed in the mid-20th century for use by a tourist attraction that rented paddle boats. In 2000, the federal government demolished a steel observation tower that offered tourists a sweeping view of Gettysburg National Military Park.

This week the nonprofit Gettysburg National Battlefield Museum Foundation reached $75 million in donations, its self-imposed target before breaking ground on the remaking of the park, and awarded a $400,000-plus contract for the stream restoration to Aquatic Resource Restoration Co. Organizers expect to seek bids for the 139,000-square-foot visitor center and museum later this year.

"We're very pleased to be at this point and that this project has become a reality," foundation President Bob Wilburn said Wednesday.

Of the donations received so far, Wilburn said, the Pennsylvania government has contributed $20.5 million, the federal government pitched in $11.9 million, and $43.6 million has come from private sources.

The new facility will be larger and better able to accommodate the nearly 2 million people who visit the park each year. The Battle of Gettysburg took place July 1-3, 1863, when Gen. Robert E. Lee's Confederate forces clashed with federal troops under the command of Maj. Gen. George G. Meade. Following the battle, the Southern troops retreated to Virginia. The storied clash left more than 50,000 soldiers dead, wounded, captured or missing.

The national military park comprises 5,989 acres and includes the Soldiers' National Cemetery, where President Lincoln gave the Gettysburg Address on Nov. 19, 1863. There are more than 1,300 monuments and 400 cannons in the park. Many of the monuments were placed by battle veterans.

The plans for the visitor center and museum include two film theaters, a book and museum store and a 250-seat snack bar. A major feature will be the restored 1884 cycloramic painting "The Battle of Gettysburg," designed to create a sense of immersion in the scene of Pickett's Charge. Known as the High Water Mark of the Confederacy, the charge involved 12,000 Southern soldiers and 7,000 Union troops. In one hour, there were more than 5,000 casualties.

The foundation also will build environmentally controlled storage for the park's collection of some 38,000 artifacts and 700,000 documents, maps and photographs, many of which had been stored in 14 unheated rooms in the basement of the current visitor center. Their deteriorating condition was a driving factor in the project. Items not on display have been moved to temporary storage on park grounds.

The Gettysburg National Battlefield Museum Foundation, based in Washington, will move to Gettysburg and operate the museum and visitor center for 20 years in cooperation with the park, after which the buildings and land will be donated to the federal government.

The planned visitor center and museum are designed to resemble a Civil War-era farm complex.