Her appearance in the battleground state comes the day after US dockworkers suspended their strike in hopes of reaching a new contract, sparing the country a damaging episode of labour unrest that could have rattled the economy.
A tentative agreement was reached to raise salaries, although other issues still need to be resolved.
Harris issued a statement saying the development "indicates progress toward a strong contract and represents the power of collective bargaining".
She added that "dockworkers deserve a fair share for their hard work getting essential goods out to communities across America".
Unions have long been a bedrock of support for Democrats but Harris has failed to secure some key endorsements.
Donald Trump says Republicans have become "the party of the American worker". (AP PHOTO)
The International Association of Fire Fighters announced this week that it would not back a candidate this year, following a similar announcement from the Teamsters.
Both unions endorsed Joe Biden four years ago.
Harris has had some support from some Teamsters locals and she won quick endorsements from US teachers unions, the building trades, the AFL-CIO and the United Auto Workers after replacing Biden at the top of the Democratic ticket.
But the divide within the labour community is a reminder of shifting loyalties in United States politics.
Democrats have increased their support among white-collar professionals while Republicans try to make inroads among voters who did not attend college.
During a rally in Saginaw, Michigan on Thursday, Trump said Republicans are now "the party of the American worker".
In a reference to labour unrest at the country's ports, he insisted that "under my leadership Americans won't have to go on strike for a better wage or a better life".
The former president also made a trip to Flint last month in an event billed as focusing on the car industry, a pillar of the battleground state.
The two candidates have been in the same cities - and in some cases the exact same venues - within days or weeks of each other.
Trump is heading to Georgia on Friday to appear with Governor Brian Kemp, the latest sign that he has patched up his rocky relationship with the top Republican in a key battleground state.
Later in the day, he is holding a campaign event in Fayetteville, North Carolina.
Union voters have traditionally leaned toward Democrats, with 56 per cent supporting Biden in 2020.
But Trump has pushed hard to win over blue-collar workers traditionally represented by some of the biggest unions.
He won 62 per cent of white voters without college degrees - although only 24 per cent of non-white voters without college degrees - in 2020.
