Is there an organization that recognizes the gravesites of union soldiers from the Civil War?

A local cemetery contains a dead union soldier. The cemetery is deteriorating and a local resident believes that there might be a group or organization that will recognize the soldier, put some flowers on the grave and maybe perform some type of ceremony. I am not aware of any such organization for union soldiers. It would probably be something like the Daughters of the Confederacy, but only for the Union.