A spokeswoman for the fund, Katie Kornfield, confirmed the death. The cause was not disclosed.
Ms. MacGregor was a veteran of the New York stage who had appeared in small television roles before being cast in “Little House on the Prairie,” a wholesome family drama based on the books of Laura Ingalls Wilder.
The show, which aired on NBC from 1974 to 1982, featured Michael Landon as Charles Ingalls, the patriarch of a family settling in rural Minnesota in the late 1800s. Melissa Gilbert played his middle daughter, Laura. (The show’s final season, from 1982-1983, was called “Little House: A New Beginning.”)
Ms. MacGregor’s character, usually known as Mrs. Oleson, debuted in the show’s second episode as the scheming and gossipy wife of the proprietor of the general store in Walnut Grove.
In a series known for its gentle pace and celebration of heartland values, Ms. MacGregor offered a peppery touch of mean-spiritedness. She held her nose in the air with a firm belief in her own superiority and had an equally spoiled daughter, Nellie, played by Alison Arngrim. She let nothing interfere with her overweening sense of self-worth, referring to her set of people as “we aristocrats.”
Condescending toward people she considered inferior — which meant almost everyone else — Mrs. Oleson believed it was her duty to raise Walnut Grove to her own standards of haughtiness, in part by teaching a fractured version of French to rustic schoolchildren. At the store she ran with her beleaguered husband, played by Richard Bull, she was reluctant to extend credit to customers.
Nipsey Hussle, a Grammy nominated rapper who sought to revive South Los Angeles, died at age 33 on March 31. Read the obituary (Matt Winkelmeyer/Getty Images for Warner Music)
Notable deaths in 2018 and 2019: Nipsey Hussle, George H.W. Bush, Stan Lee, John McCain, Aretha Franklin and other famous faces we’ve lost
In one episode, when her husband went fishing, Mrs. Oleson responded with her typical sensitivity: “Well, I declare! If you must take time off from honest work to fish, I do wish you would not leave your smelly old fishing paraphernalia in the storeroom!”
Ms. MacGregor almost turned down what turned out to be the role of a lifetime. When exploring the character, she read all of Ingalls Wilder’s “Little House on the Prairie” books, in which Mrs. Oleson is mentioned only briefly.
“It said that Nellie had a birthday party and invited the Ingalls girls,” Ms. MacGregor said in 1981. “Laura picked up a doll and Nellie had a tantrum and snatched it out of her hand and tore the dress. When Laura told her mother, she asked, ‘What did the mother say?’ ‘Nothing.’
“I based my whole character on that. What kind of mother says nothing?”
Despite her general nastiness, Mrs. Oleson was a favorite character among “Little House” viewers — the person everyone loved to hate. She was often batting her husband with her purse or rushing down the dusty streets with hoisted skirts.
Ms. MacGregor managed to find a compensatory comic quality in the role. She had an expressive, mobile face and delivered her lines with strategic pauses and points of emphasis. She was constantly taking pratfalls into mud puddles, tumbling off horses or wagons, or having water dumped on her head.
“I look for the humor of Mrs. Oleson,” Ms. MacGregor told the Associated Press in 1981. “She was originally painted as just black-and-white mean. Anyone that mean has to be a fool. So I began mixing farce into it. I think the audience counts on seeing Mrs. Oleson fall on her fanny and get her comeuppance.”
Dorlee Deane MacGregor was born Jan. 12, 1925, in Glendale, Calif., and grew up in Fort Collins, Colo. Her stepfather was a railroad worker, her mother a homemaker.
She graduated in 1947 from Northwestern University in Evanston, Ill., and then moved to New York. Known as Scottie MacGregor early in her career, she worked in television and the theater and had an uncredited role in the 1954 Marlon Brando film “On the Waterfront.” She was in touring productions of Edward Albee’s “A Delicate Balance” and “Who’s Afraid of Virginia Woolf?” before moving to Los Angeles and changing her first name to Katherine.
She had small parts in such TV shows as “Ironside,” “Emergency” and “Mannix” and was working in an art gallery when she landed her role in “Little House.”
Her marriages to actors Bert Remsen and Edward Kaye-Martin ended in divorce. She said she struggled with alcoholism and credited Alcoholics Anonymous and her faith — she became a devotee of Hinduism — with helping her recover.
She did little acting after “Little House,” but the show has remained popular in syndication for decades.
“I see myself as a good actress with good instincts,” Ms. MacGregor said in 1981. “I studied with the best teachers in the country, Sanford Meisner and Stella Adler. She taught me to go for the universal. When Mrs. Oleson falls on her rear, that’s a universal.”