People keep leaving shopping carts outside my neighborhood, who do I contact?

I live right off highway 6 near a Walmart and a home Depot, and recently there have been shopping carts piling up at the entrance of the street that leads from the main highway to our neighborhood. They're just sitting there full of trash and who knows what else and are unsightly. No one's really removed them, so who do I contact about getting rid of them? Since they aren't actually IN my neighborhood, I don't know who to call.