Protesters in front of Des Moines' main post office said the U.S. Postal Service shouldn't end Saturday delivery.
The demonstrators lined Second Avenue on Sunday. Among the protesters were letter carriers, family members and other residents from around Iowa. Similar demonstrations were held across the nation.
The Postal Service said in February that it intends to drop delivery of first-class mail to five days a week. But Congress passed a bill Thursday that requires six-day delivery.
Postal officials have said ending Saturday delivery would save billions of dollars. The protesters say Congress instead should change a 2006 law that requires the Postal Service to pre-fund future retiree health benefits.