San Antonio Mayor Julián Castro has been selected for the highly coveted role of keynote speaker at September's Democratic National Convention in Charlotte, N.C.

Castro will give the prime-time speech on Sept. 4, the first night of the convention. First lady Michelle ObamaMichelle LeVaughn Robinson ObamaAl Sharpton: Royal wedding shows white supremacy is ‘on its last breath' Meghan Markle's pre-royal 'finishing lessons' and an etiquette of equality Place your royal wedding bets: Website offers odds on surprise American guests MORE is scheduled to deliver remarks the same night.

Castro, the 37-year old mayor of the nation's seventh-largest city, has been considered a rising star in Democratic circles. Earlier this year, he sat in the first lady's box during the State of the Union address, and speculation has been rampant that he will soon angle for larger office. The keynote address is typically considered a launching pad for candidates looking for national exposure; in 2004, President Obama, then a state senator from Illinois, famously gave the keynote in Boston.

The selection of Castro should also help Democrats continue their push for Latino voters, the fastest-growing demographic group in the electorate. The president has enjoyed steady support among Latinos, and holding gains made after announcing changes to federal deportation policy earlier this year will be essential for Democrats in swing states like Colorado and New Mexico.

“As mayor, Julián Castro has worked tirelessly to move San Antonio forward by building its economy from the middle out, not the top down, by putting the city on a path to being a leader in the new-energy economy and making innovative investments in education to prepare San Antonio’s students for the jobs of the future,” said Los Angeles Mayor Antonio Villaraigosa, the 2012 Democratic convention chairman, in a statement. 

Elizabeth WarrenElizabeth Ann WarrenElizabeth Warren urges grads to fight for 'what is decent' in current political climate Tomi Lahren responds to genealogist's investigation of her family: 'She failed miserably' GOP, Dem lawmakers come together for McCain documentary MORE, the U.S. Senate candidate from Massachusetts whom many had speculated could be awarded the keynote address, will instead speak before former President Clinton on Sept. 5.