The protest organiser, the Civil Human Rights Front, which had previously organised protests that drew millions of people, had applied to the police for a "peaceful, rational and non-violent" march from Causeway Bay to Central.
Despite rally organizers not having permission to march, the park could not accommodate the crowd and many headed west towards the city's financial centre, chanting for the city's Beijing-backed leader, Carrie Lam, to step down. He's originally from Hong Kong and helped organize the event.
The demonstrators filled the streets as there was not enough space at the park.
"Peace is the No. 1 priority today, " said Kiki Ma, a 28-year-old accountant participating in the march.
"The police are doing things that are totally unacceptable", said Yim, who like numerous protesters gave only one name.
Sunday's turnout showed that the movement still has broad-based support despite the ugly scenes witnessed during the past week when protesters occupied the Chinese-ruled city's airport, a move for which some activists apologized.
Sitting on the concrete soccer fields in the Park, protesters held placards that read "Free Hong Kong!" and "Democracy now!" while holding umbrellas in the other hand to shield themselves from the heavy rainfall, Reuters reported.
"We hope that there will not be any chaotic situations today", organizer Bonnie Leung said early in the day.
Previous bans on marches have been ignored by protesters, leading to clashes with riot police. "I really hope the government can listen to us".
Public transit trains did not stop on Sunday at stations close to the protest due to overcrowding.
The majority of the crowd are dressed in black, the color scheme that has become a signature of the pro-democracy movement.
On Saturday in Hong Kong, several thousand teachers braved thunderstorms to take to the streets.
You did not mention any specific lawmaker or comments, but numerous US senators and Congress members, including House Speaker Nancy Pelosi, have affirmed the USA commitment to human rights and urged the Hong Kong government to end the standoff.
Congress also has the power to pass legislation affecting Hong Kong's relationship with the U.S.in ways that could further erode the territory's reputation for stability and rule of law. That includes the recent reintroduction of the Hong Kong Human Rights and Democracy Act in Congress, which would among its other provisions require the secretary of state to issue an annual certification of Hong Kong's autonomy to justify special treatment afforded to the city.
The former British colony has a special status, with its own legal system and judiciary, and rights and freedoms not seen in mainland China. No tear gas was used but officers said they fired one baton round.
Harley Ho, a 20-year-old social work student who attended Sunday's rally, said protesters were undeterred by the rain and would not rest until their demands were met.
Aside from Lam's resignation, demonstrators are seeking complete withdrawal of the extradition bill, a halt to descriptions of the protests as "rioting", a waiver of charges against those arrested, an independent inquiry and resumption of political reform. "In the rain, our spirit becomes stronger".
Scenes of Chinese paramilitary troops training at a stadium in the city of Shenzhen, which borders Hong Kong, gave a clear warning that mainland intervention by force is possible.