Why the barn had so many mice

The back door that allows entrance to the bank barn on the Roulette Farm on the Antietam National Battlefield.  Antietam stands as one of the key battles of the U.S. Civil War and the single bloodiest day of fighting in American history with over 22,000 dead, wounded and missing.  Over 700 of the dead from both sides of the battle were buried afterwards in the fields on and around this farm.  Sharpsburg, Maryland. 

Technical details:
Toko 4x5 wooden large format field camera.  
150mm F6.3 Rodenstock Geronar lens in Copal BT shutter. 
Ilford FP4+ shot at ISO 100. 
1/30th second at F22. 
Developed in Pyrocat HD at 1:1:100 dilution for 8 minutes @ 20 degrees Celsius in Jobo Multitank 5 with 2509N sheet film reels with drum placed on Unicolor Uniroller 352 auto-reversing rotary base. 
4x5" negative scanned with Epson V600 in two pieces and merged together in post.