Situated on the Yellowstone River, Sidney is the center of trade for the area. Oil and agriculture are the main industries, and crops include grains, sugar beets, corn, beans and hay. The Sidney area offers excellent fishing for many warm-water species, including the huge prehistoric paddlefish. You can also hunt for agates along the Yellowstone, or hunt big game, waterfowl and upland birds. Straddling the North Dakota-Montana border nearby is the Fort Union Trading Post National Historic Site.