Complex sentence: The modern American holiday of Mother's Day was first celebrated in 1908, when Anna Jarvis held a memorial for her mother at St Andrew's Methodist Church in Grafton, West Virginia, which now holds the International Mother's Day Shrine.
Split into simpler sentences: The modern American holiday of Mother's Day was first celebrated in 1908, when Anna Jarvis held a memorial for her mother at St Andrew's Methodist Church in Grafton, West Virginia. Today St Andrew's Methodist Church now holds the International Mother's Day Shrine.