ing led ▁roof ▁are ▁in ▁good ▁condition , ▁as ▁is ▁the ▁weather board ▁housing ▁that ▁protect s ▁the ▁How e ▁tr uss ▁infrastr ucture ▁from ▁the ▁elements . ▁ ▁Most ▁of ▁Oregon ' s ▁covered ▁brid ges , ▁including ▁the ▁Bel kn ap ▁Bridge , ▁were ▁built ▁using ▁the ▁How e ▁tr uss ▁system , ▁developed ▁in ▁ 1 8 4 0 ▁by ▁the ▁Massachusetts ▁architect ▁William ▁How e . ▁ ▁The ▁system ▁uses ▁heavy ▁tim bers ▁rein for ced ▁with ▁iron ▁or ▁steel ▁ro ds . ▁ ▁The ▁tr uss es ▁have ▁central ▁be ams ▁and ▁crossed ▁tim bers ▁with ▁adjust able , ▁vertical ▁iron ▁ro ds ▁to ▁support ▁the ▁struct ural ▁load . ▁ ▁See ▁also ▁▁ ▁List ▁of ▁brid ges ▁on ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁in ▁Oregon ▁ ▁List ▁of ▁Oregon ▁covered ▁brid ges ▁ ▁References ▁ ▁External ▁links ▁▁ ▁Lane ▁County , ▁Oregon ▁e G overn ment ▁ ▁Cover ed ▁Bridge ▁Society ▁of ▁Oregon ▁ ▁Category : C over ed ▁brid ges ▁in ▁Lane ▁County , ▁Oregon ▁Category : C over ed ▁brid ges ▁on ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁in ▁Oregon ▁Category : B rid ges ▁completed ▁in ▁ 1 9 6 6 ▁Category : National ▁Register ▁of ▁Historic ▁Places ▁in ▁Lane ▁County , ▁Oregon ▁Category : Ro ad ▁brid ges ▁in ▁Oregon ▁Category : 1 9 6 6 ▁establish ments ▁in ▁Oregon ▁Category : Ro ad ▁brid ges ▁on ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁in ▁Oregon ▁Category : W ood en ▁brid ges