The absence of protests before the game pleased some fans, who either saw the kneeling players as being disrespectful to the flag and the military, or were simply sick of the season-long rancour over the protests over racial injustice.
"I'm glad they stood for the anthem. It's not appropriate," said Kelly Erickson, an Eagles fan from Philadelphia who watched the singer Pink perform the Star Spangled banner without incident at U.S. Bank Stadium in Minneapolis.
President Donald Trump, for one, has been a harsh critic of the pre-game gesture, heaping scorn on the protesting players and the league for allowing them to go unpunished.
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But demonstrators who gathered outside the stadium had hoped some players would carry on with protests that began in 2016 with former San Francisco quarterback Colin Kaepernick and were joined by dozens of players around the league this season.
"All eyes are here," said Mel Reeves, a Minneapolis civil rights activist who organised a two-day "Take a Knee" conference that culminated in the rally. "When the players are doing it, people have to pay attention to the issue."
The wave of protests started to fizzle late in the season when the National Football League said it would donate $89 million over seven years to social justice causes as part of an effort to end the on-field demonstrations.
Philadelphia Eagles safety Malcolm Jenkins, who has previously raised his fist above his head, was one of those who stopped his protests.
Still, Trump stirred the issue anew last week during his State of the Union address. As the season was getting underway, he said any player who protests is a "son of a bitch" who should be removed from the field, and criticized NFL owners for failing to take action.
NFL Commissioner Roger Goodell has praised the protesters as concerned activists and said the league should work with them to address their concerns, which include the use of lethal force against minorities and racial disparities in the justice system.
As the game started, about 100 demonstrators gathered and knelt outside one of the downtown stadium's entrances, images on social media showed. Minneapolis police did not intervene, a police spokesman said.
"I think there is a lot of pressure at this stage not to do it," said activist Sandi Sherman in trying to explain why there were no protests along the sidelines.
One stop away on a commuter rail line, protesters wearing T-shirts reading "You can't play with black lives" blocked the tracks. Transit police detained 17 people who were cited for unlawful interference with transit and released, Metro Transit spokesman Howie Padilla said.
(Additional reporting by Daniel Trotta in Minneapolis; Editing by Frank McGurty and Susan Thomas)
