In the first part of the article we presented several photographs of Polish highlanders in the regional costumes, see it at Trailing of The Sheep Festival in Central Idaho with Polish Mountaineers.
Here we have some pictures of other ethnic groups present in Central Idaho. Basques are always represented in big numbers since quite many Basques live in Boise region. Basques first arrive in America with Columbus. More of them came later with Spanish colonists to South America. From there some left to California to search for gold. Eventually they ended up herding sheep in California, Nevada, Oregon and Southwestern Idaho. Here is the link to the official website of the festival: Trailing of the Sheep. Below are some photographs from 2006 festival.
I recommend Eyewitness Travel Guide to Poland (Eyewitness Travel Guides) by Teresa Czerniewics-Umer, Malgorzata Omilanowska, Jerzy S. Majewski, DK Travel Writers
This comprehensive book about Poland, showed below, may also be useful for you:
The Rough Guide to Poland by Mark Salter, Jonathan Bousfield