On the side of the Green Building is the dedication of the building to CECIL HOWARD GREEN and IDA FLANSBURGH GREEN. As clued in the poem, parts of their names are shared by other famous people. The missing names from the boxes match with the order of the names on the wall. Indexing into the other name of the famous people (i.e. first name if last name matches or last name if first name matches) and ordering by the listed numbers gives BLOOD, the answer to this puzzle and the combination for one of the locks.
|#5 Baseball Player (1963) - 5 Cecil Fielder: D||#1 Actress (1981) - 1 Bryce Dallas Howard: B||#2 Soul Singer (1946) - 2 Al Green: L|
|#4Actress (1918) - 6 Ida Lupino: O||#3 Rock Singer (1960) - 2 John Flansburgh: O|