In 1968, big group of important people who wanted to be the leader of a big group of people called the democrats got together in a big city called Chicago. Some people liked one leader called Hubert Humphrey, but other people didn't like him and wanted a different leader called Eugene McCarthy.
A lot of people didn't like the way the leaders were being picked and thought it was unfair. They wanted to tell the important people how they felt, so they made signs and started shouting outside the big building where the leaders were.
The police didn't like that the people were shouting and carrying signs, so they started pushing and hitting them. The people got really upset and tried to fight back. This made things get even more chaotic and dangerous.
The protests went on for a few days, with more and more people joining in. The police used tear gas and arrested many of the protesters. The whole country was watching what was happening on TV and some people thought it was really scary.
Eventually, the leader that most people didn't like (Hubert Humphrey) was chosen to be the Democratic nominee for president. But the protests brought attention to the fact that people wanted more say in how their leaders were picked and how they were being treated by the police.