Gavin Newsom was sworn into office as California's 40th governor beneath a tent outside the Capitol in Sacramento on Monday. 

His wife, Jennifer Siebel Newsom, along with his four children, stood by his side as he was sworn in by California Supreme Court Chief Justice Tani Gorre Cantil-Sakauye. House Speaker Nancy Pelosi and former governors Gray Davis and Arnold Schwarzenegger were also in attendance. 

The 51-year-old former lieutenant governor and San Francisco mayor takes over the top spot from Gov. Jerry Brown, who was the longest-serving governor in California's history. 

In his acceptance speech, Gov. Newsom indicated he would reach across the aisle and work for all Californians. He also renewed his pledge to make California a leading political force in the United States and the world. 

"In Washington there's an administration that is clearly hostile to California values, and California interests," Newsom said. "California has always helped write America's future. What we do today is even more consequential to what is happening in our country. People's lives, freedom, security, they all hang in the balance and the country is watching us, the world is waiting on us, and the future depends on us and we will seize the moment."

He added that Californians have the power to stand up to the political forces in Washington, "And we will."

He also renewed the charge to tackle homelessness, wealth inequality, and to bring affordable health care to every Californian. 

"I pledge to every Californian, no matter what comes at us, I will have your back," he said. "The eyes of the world are upon us now more than ever, the world needs California. This is where American's future is made. This is our charge, our calling. Now let's get to work."