The seventh-round draft pick has been outspoken and confident as his progress was watched as closely as any rookie in the league. He has been cheered by athletes and celebrities. In the end, the defensive end couldn't make a team stocked with pass-rushers.
The news was first reported by ESPN.
Sam still has a chance to get picked up by another team or to make the Rams' practice squad.
On Saturday, he attended Missouri's opener in Columbia and was introduced to the crowd at the cut down deadline in the end zone alongside defensive E.J. Gaines, a sixth-round pick who made the team.
Sam blew a kiss and waved to the crowd, then walked back to the sideline. He posed for a few pictures then started looking at his phone and headed for the locker room.
He later Tweeted about being cut, writing, "I want to thank the entire Rams organization and the city of St. Louis for giving me this tremendous opportunity and allowing me to show I can play at this level. I look forward to continuing to build on the progress I made here toward a long and successful career."
Sam added, "The most worthwhile things in life rarely come easy, this is a lesson I've always known. The journey continues."
The Rams selected Sam, the SEC co-defensive player of the year at Missouri, with the 249th overall pick out of 256 overall during May's draft. Sam came out following his final season at Missouri.
Rams coach Jeff Fisher was proud to have made the landmark pick, but he made clear from the start that he chose Sam because he thought he had the talent to make it and said his value as a player "was off the charts."
"I'm determined to be great," Sam said at his introductory news conference, packed with reporters. "I understand that right now you guys want to make a big deal of it."
From the start, teammates seemed to like having Sam around. His energy was infectious and, if there were problems, they stayed behind closed doors. Publicly, Sam was just another late-round pick trying to make the Rams, which, like other NFL teams, held sensitivity training early in camp. The Oprah Winfrey Network put off a planned documentary on Sam, saying it would allow him to focus on his dream of making the team.
At one point, Sam's Rams jersey was the No. 2 seller among rookies at NFLShop.com, trailing only Cleveland's Johnny Manziel, and Sam was among just 10 draftees selected by the NFL to be featured on commemorative coins. Sam headed to the ESPY Awards to pick up the Arthur Ashe Courage award. He got a hug from Hall of Famer Jim Brown on his way to the stage and fought back tears throughout his speech.
"Great things can happen when you have the courage to be yourself," he told the audience.
I want to thank the entire Rams organization and the city of St. Louis for giving me this tremendous opportunity and allowing me to (1/2)— Michael Sam (@MichaelSamNFL) August 30, 2014
show I can play at this level. I look forward to continuing to build on the progress I made here toward a long and successful career (2/2)— Michael Sam (@MichaelSamNFL) August 30, 2014
The most worthwhile things in life rarely come easy, this is a lesson I've always known. The journey continues.— Michael Sam (@MichaelSamNFL) August 30, 2014