▁non - sub mers ible , ▁non - overflow ▁roll er ▁gates ▁and ▁two ▁ ▁non - sub mers ible ▁overflow ▁roll er ▁gates . ▁It ▁is ▁unusual ▁among ▁the ▁upper ▁Mississippi ▁River ▁d ams ▁in ▁that ▁it ▁has ▁only ▁roll er ▁gates , ▁has ▁different ▁sizes ▁and ▁types ▁of ▁roll er ▁gates , ▁it ▁is ▁not ▁per pend icular ▁to ▁the ▁flow ▁of ▁the ▁river ▁and ▁is ▁one ▁of ▁the ▁few ▁facilities ▁that ▁has ▁a ▁completed ▁auxili ary ▁lock . ▁The ▁main ▁lock ▁is ▁ ▁wide ▁by ▁ ▁long ▁and ▁its ▁auxili ary ▁lock ▁is ▁ ▁wide ▁by ▁ ▁long . ▁In ▁ 2 0 0 4 , ▁the ▁facility ▁was ▁listed ▁in ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁as ▁Lock ▁and ▁Dam ▁No . ▁ 1 5 ▁Historic ▁District , ▁# 0 4 0 0 0 1 7 5 ▁covering ▁, ▁ 2 ▁buildings , ▁ 9 ▁structures , ▁and ▁ 1 ▁object . ▁ ▁See ▁also ▁ ▁Government ▁Bridge , ▁passes ▁near ▁the ▁lo cks . ▁ ▁Rock ▁Island ▁Ar sen al ▁adjacent ▁to ▁the ▁lo cks . ▁ ▁References ▁ ▁External ▁links ▁ ▁Mississippi ▁River ▁Vis itor ▁Center ▁Lock s ▁& ▁Dam ▁ 1 5 ▁- ▁U . S . ▁Army ▁Corps ▁of ▁Engine ers ▁Lock ▁and ▁Dam ▁No . ▁ 1 5 ▁- ▁U . S . ▁Army ▁Corps ▁of ▁Engine ers ▁ ▁US ▁Army ▁Corps ▁of ▁Engine ers ▁L D ▁ 1 5 ▁Cam ▁ 2 ▁– ▁Live ▁camera ▁of ▁Lock ▁& ▁Dam ▁ 1 5 ,