Becoming the first female surgeon in the Union Army, which woman was the only one to receive the Medal of Honor, the highest and most prestigious military award of the US government?

Medal of Honor Controversy
In November 1865, having left government service for good, Walker was awarded the Medal of Honor by President Andrew Johnson, even though she was a civilian who had never been a commissioned officer in military service.

That civilian status is why Walker's medal was rescinded in 1917, two years before she died -- along with 910 others. Walker refused to return the medal, though, and continued to wear it until she died two years later.

Sixty years after that, in 1977, President Jimmy Carter restored the honor in her name, thanks to efforts made by her family.