All these people shared one goal - to convince US politicians to finally take decisive action, including banning the sale of assault weapons.
There's something about seeing thousands of people come together through a mutual cause that restores my hope in humanity.
In the first 46 days of 2018, there were 32 shootings in America. Sixty people were killed and another 127 were injured.
When faced with numbers like that it's easy to lose hope; easy to wonder what has happened to humankind.
But when people - young, old, black, white, rich and poor - stand together for those who have lost their lives to senseless violence, I am reminded that there is still good in the world.
Gun control is an issue that divides Americans. The right to bear arms is protected under the second amendment of the US constitution and the National Rifle Association (NRA) gun lobby remains highly influential.
But there must come a point when those in power see that it is time for change. The laws in place are not working and it is about time they put the value of innocent lives above all else.
That is why people are marching. And people will continue to march, protest and stand united until something finally changes.