Chaney had the house restored, at a cost of about $500,000, to look as it did in September 1862.
The two-story white house is part of the Newcomer Farm, which Chaney owns. The farm dates to the mid 1700s.
The property was originally farmed by Christopher Orndorff who, according to family records, entertained Gen. George Washington during the French and Indian War. Later, in the 1790s, he built a new home that is now known as the Newcomer home.
The museum is on the first floor. There are two rooms for Union artifacts and one larger room for Confederate artifacts. A fourth room houses the museum gift shop.
The structure, which housed a hospital during the war, is now home to artifacts such as a sword once presented to Union Gen. George McClellan, said Annie Letizia, museum curator.
Chaney said he has more than 100 Civil War artifacts he will rotate in museum displays.
Other artifacts at the museum include letters by Robert E. Lee and Thomas "Stonewall" Jackson and a Union soldier's diary.
The Jackson letter was written the day before the Battle of Antietam to a local woman who served him breakfast, Chaney said. Chaney hopes to determine the identity of the woman, whose name is difficult to read on the letter.
"I have received the nice breakfast for which I am indebted to your kindness. Please accept my grateful appreciation for your hospitality," Jackson wrote.
Another artifact at the museum is a signed autographed picture of Robert E. Lee, of whom Chaney is a descendent.
Uniforms, engravings, weapons, paintings, prints and maps will also be on display.
The gift shop will sell books, maps, prints, educational materials, reproductions of historical documents and other memorabilia.
Antietam Battlefield Superintendent John Howard said the battlefield has no objections to having the Chaney museum on battlefield property.
"The idea of having another place where people can learn about the battle is fine with us. It is another opportunity for visitors to experience what went on here," Howard said.
About one year ago, the National Park Service purchased from Chaney approximately 50 acres and a historic barn on the farm across the street from the museum, Howard said. The National Park Service plans to restore the farm at a cost of about $800,000, Howard said.
The earliest the restoration will begin is in two years, he said. There may be interpretive displays place at the site explaining that the barn was used as a hospital during the war.
The museum and gift shop were opposed by Sharpsburg Mayor Sid Gale, Save Historic Antietam Foundation President Tom Clemens and others who said in late 2000 they were concerned commercial development on the battlefield will set a bad precedent
Chaney has said that without him the house might have fallen further into disrepair.
Some of those critics have since changed their positions after seeing the renovated home, Chaney said.
"He has done a wonderful job restoring the house. The house looks great," Clemens said.
But Gale and Clemens said this week they remain opposed to commercial development on the battlefield.
Chaney has additional plans for his battlefield property, including erecting a 11-foot statue of Lee. He dropped earlier plans for the statue and granite base to reach as high as 33 feet after objections were raised.
He may later have statues of J.E.B. Stuart and Jackson erected.
The museum is open every day from 8:30 a.m. to 6 p.m. Admission is $3. For information, call 301-432-0300.