Jim,
We have about worn out the backbone of the Sibley Guide trying to figure all the birds out!
I can get this one down to three choices.
1) Little Blue Heron - dark all over, bluish bill, Greenish legs
2) Reddish Egret (Dark Morph) - Adult should have yellow beak with dark tip, paler overall than Little Blue Heron - Juvenile has blue beak, but very pale body, dark legs
3) Juvenile Tri-colored Heron - Reddish neck, very long bill, Yellow legs.
Without seeing the legs, it is even harder to tell.
My guess is a Little Blue Heron - listed as common in MINWR, while the Reddish Egret is uncommon.
Bob & Nan