, who served as Housing and Urban Development secretary under former President Obama, announced Saturday he is running for president in 2020.
Castro, who is Mexican-American, made the announcement in San Antonio, his hometown and the city where he served as mayor for five years. He spoke in Plaza Guadalupe, an outdoor venue in the city across from Our Lady of Guadalupe Catholic Church.
"I'm running for president because it's time for new leadership, it's time for new energy, it's time for new commitment to make sure the opportunities that I had are available to every American," Castro said.
"When my grandmother got here almost a hundred years ago, I'm sure she never could have imagined that just two generations later, one of her grandsons would be serving as a member of the United States Congress and the other would be standing with you here today to say these words: I am a candidate for President of the United States of America," he said in both English and Spanish.
"There are no frontrunners that are born here, but I've always believed that with big dreams and hard work, anything is possible in this country," Castro said about his hometown.
His slogan is "One Nation. One Destiny." Castro explained that the "destiny" was "to be the smartest, the healthiest, the fairest, and the most prosperous nation on earth."
He mentioned several issues in his speech, including health care and criminal justice reform, as well as reiterating his support for "Black Lives Matter." Immigration reform was also a key topic. He mentioned, this week, and denounced Mr. Trump's characterization of a "crisis" at the border.
"There is a crisis today. It's a crisis of leadership. Donald Trump has failed to uphold the values of our great nation," Castro said.
He also said that as president, his first executive order would be recommitting to the Paris Climate Agreement, which Mr. Trump pulled out of after taking office.
He ended his speech by saying, "Let's go work! Vamonos!"
Several people spoke before Castro, including his twin brother, Rep. Joaquin Castro, D-Texas, who joked that he would grow a beard to differentiate himself from his brother. The speakers each discussed their excitement about Castro launching a presidential campaign. He was introduced by his mother.
"I want to be honest with you: There are going to be a lot of great candidates in this race," Joaquin Castro said, adding that he wished them all well, "but I know we have the best candidate with the best ideas and the biggest heart."
Castro has spent the last two years as a guest lecturer at the University of Texas and other universities and recently published a memoir that was seen as his treatise for a potential campaign. He had passed on a 2018 campaign for U.S. Senate or governor in Texas, a signeventually launching a presidential campaign.
When he formed a presidential exploratory committee in December, he told CBS News: "People are ready to get on a better track with leadership that's focused on creating opportunity for everybody and trying to bring the country together, rather than tear us apart."
"I've had a chance over the last several years to get a sense of what people are looking for. I've visited more than 100 communities across the United States and I believe they're ready for new leadership," he said.
In a field of candidates that could include dozens of current and former lawmakers, governors and mayors, Castro told CBS News last month that he would cite his "track record of getting things done at the local and the federal level."
"There are going to be a lot of talented people running and I look forward to making my case to the voters," he said.
Castro's twin brother, Joaquin, is poised to be a senior member of the House Intelligence Committee next year and to hold a senior position in his brother's campaign, likely in a fundraising role, given that both brothers have been popular draws on the county and state party fundraising circuit for several years.