Heather Cox Richardson gives the history of this day.
If you google the history of Mother’s Day, the internet will tell you that Mother’s Day began in 1908 when Anna Jarvis decided to honor her mother. But “Mothers’ Day”—with the apostrophe not in the singular spot, but in the plural—actually started in the 1870s, when the sheer enormity of the death caused by the Civil War and the Franco-Prussian War convinced American women that women must take control of politics from the men who had permitted such carnage. Mothers’ Day was not designed to encourage people to be nice to their mothers. It was part of women’s effort to gain power to change modern society.