. . . . . . but it's rather easy to find . . . . . .
1) At the published coordinates, make note of the date of the memorial.
2) Format this date as “M DD, YYYY”.
3) Translate this as “M DD, YYYY” = “a bc, defg”.
4) The cache coordinates are: N 41º (37.761 + 0.abc) W 89º (01.850 + d.efg).
This cache is part of a series – I'm sure you've figured out its theme by now.
There is a puzzle cache which completes the series.
Note that the caches are not accessible from the Interstate highway.