They will notified as soon as all awardees accept their award. They do ask awardees to accept or reject the award by a certain date so in case someone reject because they got a better fellowship, they move down the list. Once all awards have been accepted they will notify the rest of applicants.
It looks like they sent awards last week per someone who received the fellowship and announced it on Twitter. Congrats to them!
7 days agoRT @LittleBitK_Reyn: I am so excited to share that I've been awarded one of the Mellon/ACLS Dissertation Innovation Fellowship awards! Shout out to the fam & friends for gassing me up during the application process and @feMNistProf and @ehphd for their top tier support since I started this program!