To my knowledge and research, these are the 2021 50,000 watt Class A stations carrying major league baseball in English this year. There are other 50,000 watt stations broadcasting baseball but they are class B stations. Please free feel to add and/or correct. All are flagships unless noted. Affiliates may carry alternative programming at times (Blue Jays' Montreal Affiliate Hockey/Soccer). A loss from last season according to research is WFED 1500 former flagship of the Nationals. Also, WMVP is a little less favorable here than the White Sox former WGN.
660am WFAN New York Yankees
670am WSCR Chicago Cubs
680am KNBR San Francisco Giants
690am CKGM Toronto Blue Jays Affiliate in Montreal, Quebec - English Service
700am WLW Cincinnati Reds
710am KIRO Seattle Mariners
830am WCCO Minnesota Twins
850am KOA Colorado Rockies
880am WCBS New York Mets
1000am WMVP Chicago White Sox
1020am KDKA Pittsburgh Pirates*
1080am WTIC Boston Red Sox Affiliate in Hartford, CT
1080am KRLD Texas Rangers - Broadcasts when there are conflicts for KRLD-FM Flagship
1100am WTAM Cleveland Indians
1120am KMOX Saint Louis Cardinals
1140am WRVA Washington Nationals. Affiliate in Richmond, VA
*The Pirates' website mentions some games on KDKA 1020 am, all afternoon weekday games and "select" other games.