Nancy Reagan began her final journey to her husband's side Wednesday as a police motorcade carried her casket down an empty California freeway lined with saluting firefighters and mourners holding hands over their hearts in tribute to the former first lady.

The roadside reverence reflected her late husband's touch with the common man and followed some of the route his own funeral procession took in 2004, eventually winding its way up to the Ronald Reagan Presidential Library, where volunteers in blue jackets stood behind a guardrail festooned with small American flags.

The day began with a private ceremony for family and close friends at a funeral home in Santa Monica, Calif., followed by a public viewing at the library.

People came from near and far to pay tribute to the widow of the 40th U.S. president. Nancy Reagan was respected for her grace, strength and unfailing loyalty to her husband during his two terms in office and his final struggles with Alzheimer's disease.

Obit Nancy Reagan

This December 1986 file photo shows Nancy Reagan and President Ronald Reagan during a walk on the White House South lawn. (Dennis Cook/Associated Press)

Retired teacher Mary Ellen Gruendyke, who arose early so she could drive nearly 160 kilometres from her Riverside home, said she admired Reagan for her "Just Say No" campaign against drugs and the president for infusing a sense of patriotism in the country.

"Ronald Reagan was one of the best presidents we've ever had, and I admired them both as a couple for their love story and the support they showed to each other," said Gruendyke, who wore a colourful Ronald Reagan souvenir scarf around her neck.

Shuttles bused groups of mourners to take turns walking quietly in a circle around the casket covered in white roses and peonies — the former first lady's favourite flower.

The mood was sombre, and many people wiped away tears. More than 1,000 people paid their respects in the first two hours, according to the library.

The public viewing came hours after the small motorcade travelled 70 kilometres from the coast to the hills above Simi Valley northwest of Los Angeles. The public viewing was to continue for two days leading up to the funeral scheduled for Friday.

Reagan, who died Sunday at 94, planned the smallest details of her funeral. She selected the funeral's flower arrangements, the music to be played by a Marine Corps band and the list of guests invited to the private memorial.

And just as she was always by her husband's side in life, she will be laid to rest just inches from the president on a hillside tomb facing west toward the Pacific Ocean.

Nancy Reagan

Ventura County firefighters salute as the hearse carrying the body of Nancy Reagan makes its way to the Ronald Reagan Presidential Library on Wednesday. (Jae C. Hong/Pool/Associated Press)

As a heavy flow of traffic moved in the other direction, the normally congested highway lanes were wide open for the hearse as it drove beneath a massive flag hung by firefighters from an overpass.

After turning onto the Ronald Reagan Freeway, the vehicle passed under the firefighters, who wore dress blues and saluted atop their trucks. Construction workers in hard hats, riders on horseback, parents holding children and other observers lined the roadside to watch and to snap photos with their cellphones.

When the hearse arrived at the library, a military honour guard carried the casket between two identical towering portraits of the diminutive Nancy Reagan wearing a long, red dress and then past a gurgling courtyard fountain. The casket was placed in a lobby behind a bronze statue of a smiling Ronald Reagan holding a cowboy hat.

The Reagans' daughter Patti Davis, dressed in black, was among about 20 family members and close friends who attended a short prayer service beside the closed casket.

"May angels surround her and saints release her to Jesus," the Rev. Stuart Kenworthy, vicar at the Washington National Cathedral, said during a short eulogy.

The Rev. Donn Moomaw, the Reagan family's pastor, read from the 23rd Psalm, which begins, "The Lord is my shepherd; I shall not want."

Attendees included the children of Ronald Reagan's son Michael and Dennis Revell, the widower of the president's late daughter Maureen. Michael Reagan and the president's other son, Ron Prescott Reagan, are expected at Friday's funeral.

After the prayers, Davis led mourners in taking turns to pay their respects, standing quietly by her mother's casket. The final one was Reagan's spokeswoman, Joanne Drake, who fought back tears.

When the private service ended, House Speaker Paul Ryan bowed his head at the casket, made the sign of the cross and clasped his hands in prayer for about a minute.

Those who came to pay their respects tended to be older, many with memories of Ronald Reagan as both president and governor of California.

Roy Dillard, 80, drove more than 160 kilometres from Bakersfield with several generations of his family. Dillard called Reagan the greatest president in his lifetime.

His daughter, Tina Choate, said: "And he was a wonderful governor, too."

"And a great movie star in westerns," added daughter Bobbie Eldridge.

Eldridge said she most admired how Nancy Reagan "stood by her man" and the "beautiful love that they had."