The event on Saturday comes less than five months ahead of the state's caucuses - the first to take place nationwide in each presidential election, reports the BBC reported.
Of the 19 Democrats left in the running, 17 spoke on Saturday.
Former Vice President Joe Biden brought in a fire truck, bouncy house and ice cream truck for a carnival-style "Biden fest", the Des Moines Register newspaper reported.
California Senator Kamala Harris, who is of Indian and Jamaican descent, made her entry at the fundraiser dancing alongside a marching band, according to US media reports.
Senator Amy Klobuchar of Minnesota was also seen dancing and cheering accompanied by supporters wearing "Amy for Iowa" t-shirts.
Former Housing and Urban Development Secretary Julian Castro was seen grooving to the sounds of a mariachi band.
Meanwhile, Vermont and Massachusetts Senators Bernie Sanders and Elizabeth Warren focused on organising supporters, gathering voter information and knocking doors rather than big displays of support.
Saturday's Polk County Steak Fry was the largest in the event's storied history, drawing more than 12,000 excited Democrats to Water Works Park, according to the Des Moines Register.
Polk County Democrats' chairman Sean Bagniewski said organizers had sold more than 12,000 tickets, purchased more than 10,500 steaks (plus vegan options for vegan candidates Senator Cory Booker of New Jersey and Representative Tulsi Gabbard of Hawaii) and counted roughly 18,000 candidate signs scattered across the park.
"This is the biggest steak fry in history," he said.
Each candidate was given 10 minutes to speak. The only candidate not in attendance was former Representative John Delaney of Maryland, who was attending his daughter's wedding.
( With inputs from IANS )