Schlafly, an outspoken voice against the liberalism of the 1960's and 1970's, was a towering figure in what emerged as the modern religious right. Her death was confirmed by the Eagle Forum, the Missouri-based advocacy organization she led.
"Her focus from her earliest days until her final ones was protecting the family, which she understood as the building block of life. She recognized America as the greatest political embodiment of those values," the statement read. "From military superiority and defense to immigration and trade; from unborn life to the nuclear family and parenthood, Phyllis Schlafly was a courageous and articulate voice for common sense and traditional values."
Schlafly was most well-known for her work fighting the Equal Rights Amendment in the 1970's, emerging as one of the leading female critics of the feminist movement.
Schlafly, until her death, remained in the political arena and recently made the case for electing Donald Trump president. On Monday night the Republican nominee eulogized Schlafly in a statement.
"Phyllis Schlafly is a conservative icon who led millions to action, reshaped the conservative movement, and fearlessly battled globalism and the 'kingmakers' on behalf of America's workers and families," Trump said. "I was honored to spend time with her during this campaign as she waged one more great battle for national sovereignty."
In her final days, Schlafly caused consternation among some conservatives by backing Trump.
She endorsed the billionaire at a rally in her home city of St. Louis, Missouri in March, despite the fact many of her fellow travelers in the movement don't see the Republican candidate as a true ideological conservative, likening him to Ronald Reagan.
"I can remember 1980 when a lot of us didn't think Reagan was an authentic conservative," Schlafly told CNN in an interview in May.
"Reagan turned out to be best president of the century," she said. She backed Trump partly because he was the only candidate talking about illegal immigration, which she said was "the most important issue in the country."
In a statement Monday night Reagan biographer Craig Shirley called Schlafly the "First Lady" of the American conservative movement.
"Her legacy helped conservatives understand they had a choice and were not simply an echo," Shirley said. "She battled, she won, she confounded the radical left-wing feminists time and again. Frankly, she was smarter and tougher than the liberals she fought and conquered so joyously. The defeat of the so-called Equal Rights Amendment stands as but one of many monuments to her legacy."
Funeral arrangements are still being finalized, according to the Eagle Forum.