How did Memorial Day get started?

This is my question -  How and when did Memorial Day get started?

Memorial Day was officially proclaimed on 5 May 1868 by General John Logan, national commander of the Grand Army of the Republic, in his General Order No. 11, and was first observed on 30 May 1868, when flowers were placed on the graves of Union and Confederate soldiers at Arlington National Cemetery. The first state to officially recognize the holiday was New York in 1873. (resource)

Often considered the "official" start of summer in the United States, Memorial Day weekend has become a time to remember the fallen of conflicts past as well as for family picnics and trips to the beach. While parades and celebrations are now commonplace, the holiday was not universally embraced at its inception as it was initially intended to honor Union dead from the Civil War. Over time, the holiday's reach broadened until it became a national day of remembrance. (resource)

With its origins in mind, the question may be asked - how did Memorial Day begin?