The massive 500-ton cranes gently lifted the Jim Crow-era rail car high into the air.

Constitution Avenue had been closed since early Sunday morning to make way for the artifact, which was slowly lowered into the construction pit of what will become the Smithsonian’s National Museum of African American History and Culture.

Tourists, passersby and history buffs took pictures of steel and shrink-wrap and machinery. Onlookers pressed against the fences and peered through binoculars, straining to get a better view. They took pictures of themselves taking pictures of history being made, just to say “I was there.”

There to see the 44-seat Southern Railway car, which required its black passengers traveling into the pre-civil rights South to contort physically and psychically in order to conform to the smallness of their second-class citizenship.

Many were also there to see the platform and legs of a 1930s guard tower from the Louisiana State Penitentiary, known as Angola, lowered into the pit, followed by its concrete tower with a corrugated steel roof.

They were there as the museum, scheduled to open in late 2015, completed the first of perhaps 10,000 artifact installations. The nearly 80-ton rail car and the concrete guard tower — too big to be installed into a completed museum — are the only two artifacts to be put into place during construction. They’ll be part of “Defending Freedom, Defining Freedom: Era of Segregation 1876-1978,” one of 11 inaugural exhibitions. Both had been restored in Stearns, Ky., arrived at the Udvar-Hazy Center of the National Air and Space Museum on Friday and were escorted down 14th Street by police at daybreak. The crowd was young, old, racially diverse.

The museum “is something that’s way overdue,” said Hennrietta Smith, a human-resources consultant from Northeast Washington. She and her boyfriend, Keith Beale, had heard about the installation on the radio while getting ready for church. “You don’t usually see artifacts being placed, and to see it, bit by bit, it’s historic.”

“I really think it’s spiritual,” said Beale, a commercial food worker from Northeast Washington. “There are certain things you feel when you see a process like this. Just to think, what did the guards see? How were those inmates treated?”

Barbara Savarese, a clinical researcher, came in from Silver Spring to watch the installation. “I’ve been following the whole gen­esis for years and years,” said Savarese, a charter museum member. She leaned against a chain-link fence on Madison Drive, near a scaffolded Washington Monument, a block from where the newest addition to the Mall will rise. “This museum has been a long time in being built, and it’s just a milestone.”

These are artifacts “with size and substance to them,” said the museum’s founding director, Lonnie Bunch. The 1920s rail car was refurbished in 1940 and 1950 to serve Southern routes. Three-fourths of the car was for white passengers. Signs over entryways said “Colored” or “White.”

“Part of why we collected this is the recognition of how difficult it is to explain to a new generation about segregation.” It shaped black life, Bunch said. “It was not just the law of the land, it was the environment” people walked in and the myriad things that came from that.

In her poem “Train Rides,” Nikki Giovanni tells of black passengers protected by other black people as they traveled to Southern places:

“And you will sit near your fire and tell tales of growing up in segregated America and the tales will be so loving even the white people will feel short-changed by being privileged.”

Part of the challenge and the nuance of the museum is portraying the complexity of the African American experience, Bunch said. “Its not the great horrors or the great celebrations, it’s that middle that lets you know you can’t celebrate the resiliency and faith in America without understanding where that faith was tested.”

Angola, built on the site of a 19th-century plantation, today is one of the largest maximum-security prisons in the country. Run initially by a Confederate army officer, it gained a reputation for cruelty and convict-leasing, a post-Civil War practice that let private individuals lease inmates for labor. The state of Louisiana took over the penitentiary in 1901.

“The tower helps us talk about the impact of incarceration as a way to control black males in the late 19th and into the 20th century,” Bunch said. It’s also a way of talking about the effect of incarceration on the African American community. Bunch calls it an unvarnished truth that navigates the tension between what Americans want to see in a museum and what they need to know.

As the rail car, still encased in shrink-wrap, was lowered into its final position in the construction pit, the crowd broke out in applause. Kenneth Johnson, a federal auditor visiting from Atlanta who is planning to move to Washington, noted the diversity and size of the crowd.

“So many people came out to stare at a hole, but it’s more than that,” he said. “It’s history.”