In the US, we must thank Anna Jarvis, daughter of the social activist Ann Maria Reeves Jarvis, for creating "Mother's Day" here. After her mom died, Anna held a memorial service for her, then lobbied for a national holiday to honor all mothers. Congress eventually bought her idea, and the first Mother's Day transpired on our shores in 1914.
Of course, in the UK, the history of their Mothering Sunday begins at a much earlier date. (But we're accustomed to UK history being ancient compared to our country's youthful history, right?) As far back as the 1500s, “Mothering Sunday” was celebrated in the UK, but it was a Christian practice that had nothing to do with biological mothers. Rather, on the fourth Sunday of Lent, parishioners would visit their nearest big church--the one in which they had been baptized--and this church was called their “mother church."
By the early 20th century, the popularity of this Christian celebration waned. The day did not gain popularity again until American soldiers arrived on British shores during WWII and transplanted American-style Mother’s Day. Instead of focusing on a church visit, the day began focusing on showing respect to mothers. Of course, commercialization gradually entered the picture too, and offspring began bearing gifts of sweets, chocolates, flowers, and cards to their beloved mums. So, happy Mother’s Day to US Anglophiles—and happy belated Mothering Sunday to UK mums!