var ▁R ural ▁District , ▁S ard ui ye h ▁District , ▁J iro ft ▁County , ▁K erman ▁Province , ▁Iran . ▁At ▁the ▁ 2 0 0 6 ▁census , ▁its ▁population ▁was ▁ 1 3 , ▁in ▁ 5 ▁families . ▁ ▁References ▁▁ ▁Category : Pop ulated ▁places ▁in ▁J iro ft ▁County <0x0A> </s> ▁Natural ▁Pier ▁Bridge ▁is ▁a ▁steel ▁Warren ▁through ▁tr uss ▁bridge ▁sp anning ▁the ▁Clark ▁F ork ▁river ▁located ▁ ▁west ▁of ▁Al ber ton , ▁Mont ana , ▁United ▁States , ▁which ▁incorpor ates ▁a ▁natural ▁rock ▁out c rop ▁as ▁anch orage ▁for ▁a ▁pier . ▁ ▁It ▁was ▁nominated ▁to ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁as ▁part ▁of ▁a ▁related ▁group ▁of ▁historic ▁Mont ana ▁brid ges ▁known ▁as ▁Mont ana ' s ▁Historic ▁Ste el ▁Tr uss ▁Br id ges ▁and ▁achieved ▁listing ▁on ▁January ▁ 4 , ▁ 2 0 1 0 . ▁ ▁Bu ilt ▁in ▁ 1 9 1 7 ▁by ▁the ▁Lord ▁Const ruction ▁Company ▁of ▁Miss ou la , ▁Mont ana , ▁it ▁is ▁one ▁of ▁only ▁a ▁few ▁remaining ▁brid ges ▁of ▁its ▁type ▁in ▁the ▁state , ▁and ▁of ▁those ▁it ▁is ▁the ▁only ▁one ▁that ▁incorpor ates ▁a ▁natural ▁feature ▁in ▁its ▁design . ▁ ▁References ▁Notes ▁ ▁Bibli ography ▁" National ▁Register ▁Information ▁System ", ▁National ▁Register ▁of ▁Historic ▁Places , ▁National ▁Park ▁Service . ▁Retrieved ▁November ▁ 1 7 , ▁ 2 0 1 3 . ▁Ax line ,