The ordinance was first proposed after a 33-year-old Chicago man was shot at a Luke gas station around 2 a.m. on June 25. He later died at the hospital.
Hammond Mayor Thomas McDermott Jr. said violent crime is happening late at night at the city's gas stations.
"What I've noticed as mayor over the last few years is a lot of the crime taking place in our city happens afterhours and at gas stations," McDermott said. "Unfortunately, recently, we had a homicide that took place at a gas station on state line, and I thought, 'Unfortunately, we lost another life.' It was a tragic incident, and it was time to put my foot down and say, 'This is enough.'"
The ordinance closes the city's 37 gas stations from midnight to 5 a.m.
The mayor said he's gotten support from major gas stations and their owners, but not all drivers are sold on this plan.
"If they close down the gas stations, say I'm moving from Chicago to Michigan City, and the gas station is closed, it's a long stretch with no gas stations," said Sam Oatis.
The ordinance allows gas stations to petition the Board of Public Works and Safety for an exception to the rule.