Weldon, 85, had suffered from progressively worsening dementia.
Betty Weldon and her late husband, William, were longtime media leaders in Missouri's capital city.
She was owner and publisher of the News Tribune, The Fulton Sun and the California Democrat.
Besides owning newspapers, the Weldons in the 1950s guided the establishment of the city's CBS television affiliate, KRCG, which they sold in 1966.
But the Weldons were equally well-known for their horses and had a horse-breeding farm, Callaway Hills Stables Inc., near New Bloomfield.
They gave an American saddlebred to Ronald Reagan shortly before his presidential inauguration in 1981.
Weldon also served as chairwoman of the Missouri Horse Racing Commission, which was created by voters in 1984 but closed its offices in 1995 without ever licensing a pari-mutuel racing track in Missouri.
"Betty Weldon left a valuable and lasting impact on Mid-Missouri and our state," Gov. Matt Blunt said in a written statement. "Betty's leadership in print and broadcast media, her constant professionalism and her dedicated public service exemplifies Missourians' strong work ethic and heart."
Doug Crews, executive director of the Missouri Press Association, called Weldon "one of the most influential Missouri publishers of her day."
"She had the attention of the Missouri political leaders, both in the Capitol building here in Jefferson City and in Congress," he said.
Crews recalled that Weldon wielded editorial power and that candidates for statewide office would sometimes come to her seeking her blessing before making a decision to run.
"She was a powerful woman and used the power of her newspaper to get many things done," Crews said.
Weldon leaves behind a son, Frank Weldon of Jefferson City; two daughters, Lenore "Tony" Weldon, of New Bloomfield, and Sally Weldon Proctor, of Bigfork, Mont., and one granddaughter.
Tony Weldon is publisher of The Fulton Sun.
By: Newspaper publisher Betty Weldon died Wednesday after a long illness, the Jefferson City News Tribune reported.