KEENE, Calif. -- President Barack Obama on Monday dedicated the nation's newest addition to the National Park system, a 187-acre site where labor leader Cesar Chavez lived the last 22 years of his life and where he is now buried.

A crowd estimated at 7,000 came from all across California as well as other parts of the nation to witness Obama's first visit to the San Joaquin Valley on a day he called "a long time coming."

Though Chavez's home is located in the Tehachapi Mountain foothills, Air Force One landed in nearby Bakersfield, and much of the farm-labor rights movement has its roots in the Valley.

"To the members of the Chavez family and those who knew and loved Cesar; to the men and women who've worked so hard for so long to preserve this place, I want to say to all of you, thank you," Obama said.

Farmworkers were bused in from as far away as Imperial Valley to the south and Santa Rosa to the north. Children from Kern County schools were bused in. Thousands more from the Los Angeles area, the state's High Desert country, and the San Joaquin Valley - Fresno included - made the trek to La Paz, Chavez's home in this tiny hamlet.

They crowded together on one of the property's few flat areas. Based on a sustained chant of "four more years" long before Obama took the stage to speak, their political leanings were evident as well.

Los Angeles Mayor Antonio Villaraigosa, Labor Secretary Hilda Solis, Interior Secretary Ken Salazar, Chavez's son Paul and United Farm Workers President Arturo Rodriguez all spoke before Obama, with Rodriguez introducing the president to raucous applause and more chants of "four more years."

Obama in turn wasted no time in using the UFW's rallying cry: "Buenos dias," he said. "Si, se puede."

The president went on to tell the story of farmworkers and the union that rose up to fight for things such as fair pay and no pesticides sprayed in fields while they were being worked.

But Obama then said "the truth is, we would not be here if it weren't for Cesar."

He then talked of Chavez's life story and his efforts on behalf of not only farmworker rights, but basic human rights for all.

Every time someone's son or daughter comes here and learns the history of the farmworker labor movement, Obama said, they will see the road is never hopeless and the work is never done.

"Our world is a better place because Cesar Chavez decided to change it," he said.

Obama turned to Chavez's widow, Helen.

"To Helen, this will always be home. It's where she fought alongside the man she loved," Obama said. "This is the place she will live out her days."

Obama then joked, "You are our host today. Feel free to kick us out whenever you want."

Chavez's son, Paul, who heads the Cesar Chavez Foundation, preceded Obama at the podium.

"He found the place where he could plan and strategize," Chavez said of his father. "But it was more than that for my father. La Paz became a spiritual harbor for him."

The 187-acre site in the foothills east of Bakersfield is known as Nuestra Senora Reina de la Paz (Our Lady Queen of Peace), or simply La Paz. It served as the planning and coordination center of the United Farm Workers of America starting in 1971. It's where Chavez and many organizers lived, trained and strategized.

Earlier, Obama visited the grave of Cesar Chavez at La Paz. He placed a single red rose - a variety named after the labor leader - on Chavez's resting place.

The gravesite sits amid a lush garden surrounded by low, white adobe walls and arbors of dark wood beams covered in climbing vines. The grave is marked by an unpainted wooden cross and low stone marker that sits alone in the midst of a plot of well tended grass.

Obama was joined by Helen Chavez and Paul Chavez, along with UFW co-founder Dolores Huerta and UFW President Arturo Rodriguez.

Obama left the gravesite with his arms around Huerta and Helen Chavez.