Wednesday marks the 12th anniversary.
One of the people who took part in the annual "Run to Remember" 5K and 10K run and walk was Tom Hutchinson.
"Nine-eleven hit us all pretty hard and I had a friend that was on the ground when the first plane hit right in between the two towers. He's find of course but it's hitting pretty close to home you know."
After they crossed the finish line at the Capitol Mall, runners and walkers were given American flags and placed them in a memorial bordered by a white-picket fence.
Captain Michelle Eidam is with the Sacramento Metropolitan Fire District.
"It's a miniature version of the Pentagon. Inside is a name plate with each person's name who lost their lives, all 3,000. And there's a little peg next to each one where their flag can be placed. And at the end of it we've got this beautiful memorial of 3,000 flags flying in this pentagon."
Proceeds from the registration fees that people paid to take part in yesterday's "Run to Remember" will go to various charities including widows and orphan funds for police and firefighters.