The Mackinac County Sheriff's Office says the roadway was fully reopened at approximately 2:30 a.m. on Saturday.
Two separate accidents in Mackinac County Friday afternoon forced the closure of northbound I-75 for about an hour.
The accidents happened about 15 miles north of St. Ignace.
One crash involved a passenger car, the other a semi carrying 12,000 gallons of propane.
Both drivers suffered minor injuries. The sheriff's department said both vehicles went out of control in white-out conditions.
There were no reported propane leaks.