(CNN) Black Lives Matter activist DeRay Mckesson filed to run for mayor of Baltimore on Wednesday night, joining a crowded Democratic primary race hours ahead of the registration deadline.

"It is true that I am a non-traditional candidate -- I am not a former mayor, city councilman, state legislator, philanthropist or the son of a well-connected family," Mckesson said in a Medium post announcing his candidacy. "I am an activist, organizer, former teacher and district administrator that intimately understands how interwoven our challenges and our solutions are."

"I am," he wrote, "a son of Baltimore."

Known simply as @deray to his nearly 300,000 Twitter followers, Mckesson, 30, is a Baltimore native who rose to prominence during the demonstrations in Ferguson, Missouri, following the police killing of unarmed teenager Michael Brown in 2014.

Since then, he has traveled the country to protest, organize and speak out against police abuse and racial inequality, chronicling it all on social media.

In this presidential cycle, Mckesson has met with both Hillary Clinton and Bernie Sanders as part of a broader effort to lobby for the end of "broken windows" policing and an increase in local oversight of police departments.

This new campaign, which he said on Wednesday will address issues "more expansive than policing," puts the Black Lives Matter movement, along with his Campaign Zero group, into uncharted territory -- electoral politics.

Mckesson has less than 90 days to make his case to Democrats, who have a number of high-profile candidates on the 2016 primary ticket, including former Mayor Sheila Dixon and City Councilman Nick Mosby, husband of Baltimore City State's Attorney Marilyn Mosby, the prosecutor in the Freddie Gray case.

Mayor Stephanie Rawlings-Blake announced in September of last year that she would not seek reelection.