The wife of Democratic presidential candidate Bernie Sanders on Monday spent time with some Americans whose ancestors were around a long time before there was a United States.

"It's interesting that the native Americans haven't been at all at the center of any discussion for ages," Jane Sanders said before speaking to a town hall rally in Casper.

She was stumping for her husband, who defeated rival Hillary Clinton to win the Wisconsin primary.

"We owe them a debt of gratitude for protecting the land, for their concern about the environment," Sanders said.

Monday, she met with the vice chairman and a couple members of the Northern Arapahoe Tribe. She and her husband visit tribes to listen and not seek endorsements, she added.

They talked about natural gas fracking and its effects on water pollution near Pavillion, other water issues, education and health care, she said.

The Sanders' interest in Indian issues began in Nevada last year with another environmental controversy when a young woman spoke at a rally about Oak Flat, Ariz., which was formerly on Apache land and is considered to be a sacred site.

A Department of Defense bill allowed a foreign mining company to come in and mine copper, and now more than 400 tribes oppose it, Sanders said. "They're fighting it."

That was the first Indian-related site she visited to talk to tribal members, she said. "It sounded really important."

Since then, she and her husband have met with Native American tribes across the country including Alaska, Hawaii, Minnesota and Arizona, Sanders said.

"Just hearing about the systemic racism, about treaties that have been ignored, about water rights, about mineral rights, about inadequate health care, and inadequate housing and education," she said. "And we think that's something we need to pay attention to."