Armstrong Mayor Greg Buum gave his written resignation, city attorney David Stein announced at a Monday night City Council meeting.
The Iowa Attorney General's Office has charged Buum, the town's police chief, its city clerk and two former clerks in an alleged plot to loot the city coffers and cover it up.
Buum, 69, also is charged with misusing a saw from the Northwest Iowa town's volunteer fire department in his personal business.
Free on $67,000 bond, he declined to comment on the charges he is facing when reached at home Monday.
"Nope, not talking to anyone," he said. "Thanks for the phone call."