The San Francisco Chronicle's Susan Slusser was first to the news, and suggested Maxwell's decision came as a reaction to Donald Trump slamming National Football League player protesters as "sons of bitches" who should be "fired". Teammate Mark Canh was seen placing his hand on Maxwell's shoulder.
Prior to the game, Maxwell denounced President Donald Trump on Instagram and Twitter.
Maxwell appeared to be moved to kneel after being troubled by President Trump's "son of a b--" comment Friday night about those who kneel in the NFL.
After Maxwell took a knee the A's displayed a message at the Coliseum, saying "The Oakland A's pride ourselves on being inclusive".
"Yeah, f-- this guy!"
"Inequality is being displayed bigger than ever right now as our president shows that freeedom (sic) of protest and speech is not allowed.", Maxwell wrote in another tweet. "(Expletive) this man! Seriously on the highest platform for our country expressing that it is OK for there to be Division of man and rights!"
Other football players have followed suit, but Maxwell is the first baseball player to kneel during the anthem.