RAPID CITY, S.D. (KELO) --Thousands of people from around the world gathered in Custer State park this morning for the 59th annual Buffalo Roundup.  Over 20,000 people were in Custer to watch as the bison made their way in together. "It's the 15th year I've been out here in a row and I love it. Where else are you going to see the American Bison like you see here, and all the conversations. I've been talking from the time I get here until the time I leave. Yeah, I plan on doing this for another 15 years or more if I have any say," Wisconsin visitor Dan Stroobants said. "It's an adventure, it's a team effort. We have over 200 staff that come from all across the state, all across the department to help us out and they're helping park cars, doing maintenance, medical from down here, as well as the arts festival we have going on and on average we see about 20,000 visitors at this event," Custer State Park Visitors Center Supervisor Lydia Austin said. The richest rodeo in South Dakota is now even richer This year's class saw over 1,400 bison make the run on this roundup and it was a little bit slower than normal due to the heat. "Yes it took longer, people are getting to take videos with their cameras, you got to enjoy it a lot more. It wasn't, you blinked and it was over, so this was beautiful. Like I said, I plan on doing this for a long time," Stroobants said. This process is necessary to help maintain a safe number of bison in the park. "This is a yearly event that regardless if the public showed up. It's a management tool for our buffalo. Our park can only sustain so many animals, so every year we round them up, get the numbers down so we can auction some off and then we also do health checks and brand them to stay in the state," Austin said. The calves get branded and receive all of their vaccinations. While the females also receive pregnancy checks to make sure they are healthy. Custer State Park normally has just over 900 bison throughout the winter months after this event.