Houston Police Chief Art Acevedo asked residents to avoid the South Loop 610 at Kirby due to the amount of traffic participating in the event.
"We just want to keep people safe," Acevedo said in a live stream of the parade. "There are a thousand vehicles here that will be looping."
The South Loop came to a standstill during the parade near Almeda as the line of cars stretched for miles. The congestion was made worse by road construction and at least one crash, Acevedo said.
As the lead vehicle of the parade approached I-45 and US-59, Acevedo reported the tail end of the parade had still not left Fannin and 610 South Loop, a distance of around 7 miles.
Sunday's rolling rally was the latest organized in support of the campaign and appeared to go on without any major incidents.
That was in contrast to a 'Trump Train' incident in Central Texas late last week, as cars adorned with Trump flags surrounded a Joe Biden campaign bus in Hays County.
RELATED: Biden camp cancels multiple Texas events after a "Trump Train" surrounded a campaign bus
The FBI is investigating that incident that included a minor collision between two vehicles in that caravan.
Texas is being considered a 'toss-up' state in Tuesday's 2020 presidential election by some prognosticators, a projection that was promptly dismissed by participants in a similar parade on Friday.
"I can't believe they think it's so close," a Memorial Drive parade participant said. "There is no way Trump isn't going to take this all the way to The White House again. I think it will be a landslide."
SEE ALSO: Hundreds ride in President Trump parade on Memorial Drive