"It's an important time in our nation's history and it's also an important time for the folks in our district," Whitesides, a Democrat and former NASA chief of staff, said in an interview with ABC7.
"We need to make sure that we're continuing to grow jobs in our district, we need to make sure we're protecting Social Security and protecting a woman's right to choose," he said. "This is a very important time and I'm looking forward to serving."
Whitesides had the support of national Democrats in his successful effort to unseat Republican incumbent Rep. Mike Garcia.
Garcia conceded Monday, saying he had congratulated Whitesides and would ensure a smooth handoff. Whitesides said that he had spoken with Garcia and thanked him for his service to the district and the nation. He said he would fight in Congress for good jobs and lower household costs.
CA's 27th congressional district switching to Democrats after Garcia concedes
Whitesides, who is also a former CEO of Virgin Galactic, said during the campaign that he would use his business experience to solve problems. He spotlighted Garcia's opposition to abortion rights, calling him an extremist.
The last Republican congressman anchored in heavily Democratic L.A. County, Garcia, a former Navy pilot who flew over 30 combat missions during Operation Iraqi Freedom, had displayed a surprising ability to beat the odds in a district with an 11-point Democratic registration edge.
The once-conservative 27th District runs through suburbs and high desert. Garcia, a supporter of former President Donald Trump with a conservative voting record, first won election campaigning against California's liberal-leaning government: "I don't want my country to turn into what my state has become," he said at the time.
The Associated Press contributed to this report.