"If the 20th century was the age of the automobile, there's no more iconic car than the JFK convertible," said noted historian Douglas Brinkley. "It's the one artifact of the Kennedy assassination that kind of reigns supreme."

The 1961 four-door Lincoln Continental limousine that President John F. Kennedy was riding in on Nov. 22, 1963, when shots rang out in Dallas' Dealey Plaza is one of the most popular exhibits at the Henry Ford Museum in Dearborn.

The Dearborn history center — which includes the Henry Ford Museum — is marking the 50th anniversary of Kennedy's assassination with a free museum day on Friday sponsored by Target and two impressive sold-out programs on Monday and Tuesday night.

The customized Lincoln, which was refurbished after Kennedy's death with new features such as titanium armor and a permanent top, has a historic value and emotional power that can't be underestimated.

Author James L. Swanson, who'll join Brinkley and former CBS News anchor Dan Rather at a Monday night panel discussion at the museum, Henry Ford Museum, says he's almost intimidated by the thought of seeing the artifact in person for the first time.

The car evokes haunting what-ifs, according to Swanson, whose new book, "End of Days," is a minute-by-minute account of that day in Dallas. "What if the bubble top was on? What if the car had moved faster? What if the car had accelerated after the first shot? What if the driver had swerved after the second shot?"

A car to match

Every car tells a story. The one that carried Kennedy on his last day alive speaks of tragedy as well as the happier days of his White House administration and the eternal truth that, even after devastating loss, life goes on.

Sleek and confidently modern for the times, the 1961 Lincoln Continental represented a break from the past, just like the very forward-looking presidency of Kennedy.

"That was the year Lincoln introduced brand-new styling, really a fresh, clean-looking car compared to the big chrome ducks that had been popular in the '50s," said Matt Anderson, curator of transportation at the Henry Ford. "It was just a perfect complement for the president, because he was a young man coming into office and had his bold vision for the New Frontier."

The Lincoln was assembled in early 1961 at Ford Motor Co.'s Wixom plant and would have retailed for about $7,300. But to fit the needs of a VIP limousine, it was customized by Hess & Eisenhardt of Cincinnati. The changes included adding 3-1/2 feet of length, which made room for jump seats, and redoing the interior with plush appointments.

The modifications — which also included the portable roof system, a hydraulic rear seat and steps on the rear bumper for Secret Service agents, among many features — pushed the car's cost to nearly $200,000. Ford retained ownership of the limo, leasing it to the White House for $500 a year. Code named X-100 and SS-100-X, it looked gleaming in photographs with its midnight blue paint with a metallic shimmer — just the ticket for a handsome, well-dressed, media-savvy leader.

"I've heard it was painted that color so it would show up better on black-and-white television in those days, which makes sense because it does look nice if you look at the old news footage," Anderson said.

The comfortable, stylish car flown to Texas in 1963 for a trip to heal Democratic Party squabbling before the 1964 election was not equipped in those more innocent times with the mandatory security features of future presidential limousines.

The convertible's famous bubble top, "a series of transparent roof panels ... that you could put on the roof for protection from rain, wind, what have you" was a convenience only, according to Anderson. "They were not bulletproof, just meant for inclement weather."

Kennedy disliked the bubble top and having Secret Service agents riding on the car. Swanson, for one, said he thinks the bubble top could have made a difference if it had been used that sunny afternoon in Dallas, even without being bulletproof. "Certainly, when a high-speed bullet strikes any surface, it can shatter and deflect," he said.

But what-might-have-beens don't change the fact that Kennedy suffered a massive head wound that was unsurvivable, a moment captured on film by an amateur camera operator named Abraham Zapruder.

Suddenly, a tour of Texas cities became the day that changed America forever. And when images from the Zapruder frames and, eventually, the film itself, reached the public, the violence that happened in that car was seared into the collective consciousness.

Back in commission

When Clint Hill appears at the Henry Ford Museum for Tuesday's sold-out event, it will reunite him with the vehicle that he leaped upon to protect a stunned Jacqueline Kennedy, who was sprawled on the rear of the car, reaching, by some accounts, for a piece of her husband's skull.

Later, when the limousine had arrived at Parkland Hospital, the first lady wouldn't move from her crouch over her husband until Hill, sensing her reason, took off his jacket and covered Kennedy's head with it.

After the assassination, the X-100 returned to Washington, D.C., in its cargo plane. The car was scoured for information and clues by the FBI and Secret Service, Anderson said.

From the slowness of a turn on the motorcade route to a crack in its windshield, details linked to the car have continued to be scrutinized and provide fodder for conspiracy theories. The original size, shape and details of the car became — and remain — a key piece of forensic evidence.

In late December 1963, Anderson said, the car was sent to Hess & Eisenhardt for a thorough security revamp called the "Quick Fix" project, which cost $500,000. By spring 1964, the limousine — now with an extensive makeover that ranged from armoring the car's body to retrimming the interior and adding a permanent top — went back to the White House motor pool.

Although the move seems hard to comprehend now, the planning and production of a new parade limousine could have taken so long that a panel of experts decided "the simplest, most practical alternative was to rebuild this car," Anderson said.

Tales abound about its second incarnation — such as President Lyndon Johnson's displeasure that the revamped car still had Kennedy's midnight blue shade. LBJ had it repainted a somber black.

Johnson wanted and, in 1967, got a roll-down window for the car-turned-fortress, while Richard Nixon eventually had a hatch added to the roof. "I guess it's hard to say no to the president," Anderson said. "There are photos of President and Mrs. Nixon standing through it waving to the crowds, which completely eliminates any advantages of the security of the car."

The refurbished limousine was used occasionally by presidents until being retired in 1977. It was donated by Ford to the museum and officially joined the collection in 1978, according to Anderson.

Emotional power

An early 1980s photo of the JFK limousine shows how it was displayed behind tall transparent panels that were more isolating than the low metal fence that surrounds it today. Then and now, there has been sensitivity to displaying it with respect and understanding the feelings it would evoke.

Donna Braden, a curator of public life at the Henry Ford Museum, has delved into the impact of the car on observers. "I sat there watching people once during a study we did to see who stopped, how long they stopped and that sort of thing. It was very interesting because people who remembered it seemed to have a very personal connection to it and stopped talking to their kids and grandkids because it's too emotional to explain in an intellectual way."

Much like funerals and monuments, objects like the JFK car can play a role in the processing of a national tragedy.

"I think it makes it real in a way that's helpful and it becomes a place where people can talk about it, have dialogue about it and help understand. It sort of creates a community around an event, the therapeutic quality of feeling like you're not alone," Braden said.

The enduring emotion of the JFK car is acknowledged even by assassination researchers such as Milford's Dale Myers, who can recite chapter and verse about the car's original details.

Myers used the Warren Commission Report's measurements of the car in his computer animation of the assassination used at the 40th anniversary for a two-hour ABC News investigation that supported the case for a lone gunman, suspect Lee Harvey Oswald.

"Most people don't care it's been rebuilt," said Myers, author of "With Malice: Lee Harvey Oswald and the Murder of Officer J.D. Tippit."

"It has the power for the average American and even for me, I guess. The frame of the car, it is the real deal, even if it was cosmetically altered for reuse."

Last week at the Henry Ford Museum, that power was almost palpable. Brother and sister Bob Urbanic, 64, of Ann Arbor and Karen Stulck, 66, of Boston, the Kennedy family's hometown, recalled finding out about the assassination in high school.

Seeing the car made Urbanic think about "just the tragedy of taking a life in a brutal way."

Rob Zagar, 57, of Des Moines described seeing the limousine as surreal. He said he felt almost guilty about taking a picture of "a huge piece of history."

Brinkley said he thinks the 50th might be the last landmark anniversary where a number of people with direct connections to the events of the assassination are still around to share stories and give oral histories. The true memory of the event may fade a little with time, but not the fascination.

"John F. Kennedy is always going to be the young, handsome president gunned down in his prime. We all get older and Kennedy never does," Brinkley said. "So that car will be of interest to people hundreds of years from now. It was a seminal moment in American history, and the car at Henry Ford is the iconic symbol of that ghastly day."