Firehouses are cool and do are "dogs"! Go to the posted coords and you will see a firehouse that has a memorial with three plaques on it. Each one has a date on them that you will use to solve for the final which can be found at N40 15.ABC W74 44.DEF.
From the plaque on the left:
A = First digit of the day.
B = Third digit of the year.
From the plaque in the middle:
C = First digit of the day.
D = Third digit of the year minus the first digit of the year.
From the plaque on the right:
E = Fourth digit of the year minus the first digit of the day.
F = Fourth digit of the year minus the second digit of the day.
Checksum: A+B+C = 9 D+E+F=11
Hopefully you get the connection between the posted coords and the final! ;-)