Mileposts are used literally to indicate distance on roads especially in rural or less populated areas. Just after milepost 27, turn left onto the gravel road.
Pro Tip 2/3
Travel Progress
Mileposts help track progress on a journey, showing how far you've come or how much further to go. They cheered when the car passed the milepost marking halfway to their destination.
Pro Tip 3/3
Not for City Travel
Mileposts are rarely found within cities; they are more common on highways and country roads. You won't find a milepost on city streets, they are for longer distances.