It wasn't started by Hallmark, you know...
From Mothers Day History :
"The earliest tributes to Mother's Day date back to the annual spring festival the Greeks dedicated to Rhea, the mother of many deities, and to the offerings ancient Romans made to their Great Mother of Gods, Cybele.
Christians celebrated a Mother's Day of sorts during a festival on the fourth Sunday in Lent in honor of Mary, mother of Christ. In England the holiday was expanded to include all mothers. It was then called Mothering Sunday.
In the United States it started with one woman named Anna Jarvis. Jarvis was an Appalachian homemaker and she organized a day to raise awareness of poor health conditions of her community. She thought the day would be best advocated by mothers and called the day 'Mother's Work Day'.
When Anna Jarvis died in 1905 her daughter, also named Anna, began a campaign to memorialize the life work of her mother. Anna remembered that her mother said there were many days dedicated to men but not for mothers. Anna then began to lobby the politicians of the time to support a day dedicated to mothers. Anna Jarvis talked to many politicians including Presidents Taft and Roosevelt hoping they would support her campaign.
Jarvis organized a church service to celebrate her mother in 1908 and Anna handed out white carnations to those in attendance because the white carnation was her mother's favorite flower. Anna Jarvis' hard work began to pay off five years after that service in 1913. The House of Representatives adopted a resolution calling for officials of the federal government to wear white carnations on the day many began calling Mother's Day, the second Sunday in May.
Finally on May 8, 1914 President Woodrow Wilson signed a Joint Resolution designating the second Sunday in May as Mother's Day.