Author: David Agren, Special to USA Today

The caravan stretched for miles as migrants ambled along the Coastal Highway in southern Mexico still more than 1,000 miles from U.S. border

Here’s what you need to know about the migrant caravan, from who is making the journey to why they’re going north.

The number of migrants, says Mexico, has dropped to about 4,500 from more than 7,200. Nearly 1,700 migrants remained in Mexico to seek asylum.