The one-day service cutback is an attempt to help save the financially troubled U.S. Postal Service, which is billions of dollars in the red.
But letter carriers who gathered Sunday in Seattle said six-day delivery means job security, and they fear any cutbacks would ultimately mean and end to door-to-door delivery altogether.
They hope to send that message to Congress.
"Ending Saturday delivery doesn't save the post office - it's just the beginning of the end," said one postal worker, Garrett Scott.
He and the others were responding to a recent announcement by the postmaster general that six-day delivery would end in August. Under the plan, first-class mail would only be delivered to homes and businesses five days a week.
Package delivery would continue six days a week. And post offices that are currently open on Saturday would remain open on that day under the plan.
But not everyone thinks that elimination of Saturday home delivery is such a bad thing.
"I think it's a good idea if that's what they've got to do to fix the problem," says Daniel Rivera.
Christina Viera, who also supports the Saturday service cutback, says she will hardly notice the change.
"I don't even hardly send anything," she says. "I have a business, but I send checks in the mail for that. But personal stuff I do it all online and it's free."
According to the U.S. Postal Service, package delivery has increased 14 percent since three years ago - while first-class mail has plummieted.
"Everywhere you go there are cuts necessary, and I'm not going to miss one day of mail delivery," says Joshua Rowland, who supports the Saturday cutback. "If we have to do some kind of fiscal balance, let it go."
Ending Saturday mail is expected to save $2 billion annually - but letter carriers say it's not enough to save the Postal Service. They argue that eliminating Saturday delivery would mean lost revenue from customers who work with the Postal Service.
"Cutting Saturday delivery doesn't save the Postal Service - it hurts," says Scott. "Americans have a right to good quality service six days a week, and we can't afford to lose jobs."