Sandra Day O’Connor, the first woman to serve as a justice on the United States Supreme Court, has announced she is withdrawing from public life.

A critical swing vote for much of her tenure, O’Connor, an Arizonan who was appointed by President Reagan, announced that she was told she had early-stage dementia “some time ago” and that doctors believed it was most likely Alzheimer’s disease.

“How fortunate I feel to be an American and to have been presented with the remarkable opportunities available to the citizens of our country,” wrote O’Connor. “As a young cowgirl from the Arizona desert, I never could have imagined that one day I would become the first woman justice on the U.S. Supreme Court.”

You can read her letter addressed to the American people here:

Sandra Day O’Connor Letter

O’Connor said she would keep living in Phoenix, where she returned when she left the court in 2005.

“I hope that I have inspired young people about civic engagement and helped pave the pathway for women who may have faced obstacles pursuing their careers,” wrote O’Connor. “My greatest thanks to our nation, to my family, to my former colleagues, and to all the wonderful people I have had the opportunity to engage with over the years.”

Her husband, John J. O’Connor III, died in 2009 after a battle with Alzheimer’s disease, and his diagnosis was a large factor in her decision to retire from the Supreme Court.

Her son Jay O’Connor told the AP that his mother, like many who reach their upper 80s, began to have challenges with her short-term memory.

That made some public events more difficult. Hip issues have meant she now primarily uses a wheelchair.

Over about the past year, O’Connor and his brother Brian cleared out O’Connor’s Supreme Court office and went through hundreds of boxes of files and other items she had in the building’s basement.

A gavel used at her 1981 confirmation hearing, her Presidential Medal of Freedom and T-shirts made annually by an exercise class she started at the high court are among the items O’Connor has now donated to the court’s collection, the Library of Congress and the Smithsonian.

An Arizonan who was recommended for the Supreme Court by Sen. Barry Goldwater, O’Connor was a state court judge before being unanimously confirmed to the Supreme Court at 51.

She had graduated third in her class from Stanford Law School and was the first woman to lead the Arizona state senate.

Chief Justice John G. Roberts Jr. said today that Justice O’Connor was a “towering figure in the history of the United States and indeed the world.”

“She serves as a role model not only for girls and women, but for all those committed to equal justice under law,” Chief Justice Roberts said in a statement after the announcement.