"Wearing a mask is not a political statement".
The mandate states that "every person working, living, visiting, or doing business in the City of St. Augustine shall wear a face covering in any indoor location, other than their home or residence, when not maintaining social distancing from other person (s), excluding family members or companions". His stance made the north Florida city an attractive location to Trump, who has mostly refused to wear one.
The Republican National Committee moved most of its convention from Charlotte to Jacksonville, Florida, in part because President Trump did not want delegates wearing masks.
The city's mayor, Lenny Curry, was not present at the news conference.
Trump is now set to accept the nomination at the city-owned VyStar Veterans Memorial Arena in Jacksonville, which holds 15,000 people.
Jordan Elsbury, the city's chief of staff, said officials came to the decision after speaking with Jacksonville hospitals.
The letter, signed by about 200 doctors, states that Florida is already considered a hot spot for the virus. The letter, which was delivered to Curry this past weekend, also urged officials to require masks.
"It is extremely risky and contrary to current public health recommendations to stage a large event in an area where the number of cases is surging", the doctors wrote. "The RNC should be postponed or very significantly reduced in numbers because of these risks", the open letter states.
President Donald Trump believes the decision to wear a mask to help prevent spreading the deadly coronavirus, now infecting record numbers of people in many places in the United States, is personal, White House Press Secretary Kayleigh McEnany said on Monday.
Florida Gov. Ron DeSantis was asked by CNN's Natasha Chen on Sunday if he has assured Trump that the convention can take place without mask requirements, after DeSantis said residents should stay away from closed spaces, crowds and close contact - what he calls "the three C's".
He encourages people to make whatever decision is best for their safety.