From 1828 to 1867, the Fort Union Trading Post, located between Sidney, Montana and Williston, North Dakota, was the longest lasting designated space for economic and social exchanges between Northern Plains tribes and cultures from around the world. As many as 11 tribes traded here, and they would provide the furs from animals that they would collect in the winter when animal furs were at their thickest," Alice Hart, the National Park Service site superintendent, said last week. "There were items that came in from all over the world from Italy and China, England, all over Europe. The fort is surrounded by large walls, once meant for protection, but Hart said all the exchanges were peaceful. "This was the most prominent fur trade post in the nation here on the Upper Missouri River," Hart said. "You can imagine as you approach the place that if this was the only built structure on the landscape for hundreds and hundreds and hundreds of miles, this would have been a very, very impressive sight to see." People lived, worked and raised their families at the trading post for the nearly 40 years it was open."It was torn down when the Army got out here in 1867. This is all rebuilt on the original foundation stones same site, same size," said National Park Service ranger David Carr while giving MTN News a tour of the area. Carr and the other rangers working will take visitors on free tours of the fort. Walking guides are also available. "Steamboats came up from St. Louis once a year, usually with the June rise. They dock out front, they drop off anywhere, depending on the size of the ship, anywhere from 50 to 200 tons of cargo (then) squeeze on 50 to 200 tons of fur, head back down to St. Louis the next day. Average is about two months coming up here, two weeks getting back," Carr said. The Missouri River was once right on the edge of the trading post. "It's been 200 years almost since we were founded. And the river is now the confluence of the rivers is now a couple of miles away. But it was very near here. And that was the highway of the time," Hart said. Now, the trading post has a small museum, story and events to learn all about what the times were like when the post was thriving. "Nothing really traveled faster than a man on a horse, or a boat on a river, is how long things took to move around, which is so different. And I love it if people reflect on how different time was and how long things took, communications, exchanges, all of that," Hart said. "A lot of the parks these days are really, really crowded, a lot of the big parks. And we're not very crowded and we have a great story and it's incredibly important in American history, incredibly important in the northern plains."The site, which now sits in two states, four counties and two time zones, sees around 14,000 visitors every year. "We want people to know about this story. We want people to know historically how important this location was," Hart said.