[Vehicle] wheels cut solid rock, carving a memorial to Empire Builders. What manner of men and beasts impelled conveyances weighing on those grinding wheels? Look! A line of shadows crossing boundless wilderness.
Foremost, nimble [vehicles], come poised Mountain Men carrying trade goods to a [commodity] fair - the [event]. So, in [date], [leader] turns the first wheels from [location] to the Rocky Mountains! Following his fain trail, a decade later and through the [decades], appear straining, twisting teams of [vehicles] for [location] pioneers. Trailing the [location]-bound avant-garde but otherwise mingling with those emigrants, inspired by [belief] fervor, loom footsore and trail-worn companies - [sect] dragging or pushing [vehicles] as they follow [leader] to the Valley urging [vehicles] to extremity, straining resources and often failing, hurry [persons] [location] bound.
A different breed, not emigrants but enterprisers and adventurers, capture the [era] scene. They appear, multi-teamed units [pulling], - heavy [vehicles] in tandem, [drivers] delivering freight to [event] outposts and agencies. Now, the apparition fades in a changing environment. Dimly seen, this last commerce serves a new, pastoral society; the era of the [commodity] baron and the advent of settlement blot the [route].