Definition of "pack train"

Shortly after six, our pack train arrived. […] We had nineteen serving men and twenty-six pack mules! It was a perfect caravan.

1869, Mark Twain, chapter 41, in The Innocents Abroad

Here they met a pack-train of burros that came down the mountain trail.

1914, Zane Grey, chapter 9, in Light of the Western Stars

In Italy's rugged mountains, mules and horses can go where a jeep can not go. […] Each pack train has its own veterinarian to give first aid.

1944 June 12, “Medicine: War-Horse Hospital”, in Time, retrieved 24 May 2015

Muybridge […] would travel through the Western landscape with as many as four assistants and a pack train to carry his glass negatives and chemical preparations and cameras.

2003 March 8, Edward Rothstein, “The Photographer Who Found a Way to Slow Down Time”, in New York Times, retrieved 24 May 2015