. S . ▁st amps ▁until ▁ 1 8 9 0 . ▁P ict orial ▁designs ▁did ▁not ▁appear ▁on ▁st amps ▁for ▁ordinary ▁mail ▁until ▁ 1 8 9 3 : ▁and ▁those ▁issues ▁were ▁carefully ▁promoted ▁as ▁a ▁special ▁series ▁in ▁honor ▁of ▁that ▁year ' s ▁Columb ian ▁Ex position — one ▁that ▁would ▁soon ▁disappear , ▁leaving ▁national ▁hero es ▁as ▁the ▁sole ▁subjects ▁for ▁definit ives . ▁It ▁was ▁not ▁until ▁the ▁series ▁of ▁ 1 9 2 2 – 2 5 ▁that ▁the ▁Post ▁Office ▁again ▁placed ▁pictures ▁on ▁definit ive ▁st amps — conf ining ▁them , ▁however , ▁to ▁values ▁of ▁ 1 5 ▁c ents ▁and ▁above ; ▁the ▁lower ▁denomin ations ▁still ▁presented ▁the ▁normal ▁port ra its ▁pres idents ▁and ▁other ▁famous ▁Americans . ▁ ▁The ▁ 1 8 6 9 ▁p ict orial s ▁had ▁a ▁brief ▁moment ▁of ▁re - ex pos ure ▁when ▁repr ints ▁of ▁them ▁appeared ▁in ▁ 1 8 7 5 ▁( the ▁Post ▁Office ▁that ▁year ▁repr int ed ▁many ▁of ▁its ▁old ▁issues , ▁int ending ▁to ▁display ▁every ▁U . S . ▁post age ▁stamp ▁ever ▁produced ▁in ▁its ▁exhib it ▁at ▁the ▁Philadelphia ▁Cent enn ial ▁Ex position ▁in ▁ 1 8 7 6 ). ▁In ▁contrast ▁to ▁the ▁re jection ▁these ▁designs ▁met ▁in ▁ 1 8 6 9 , ▁cent enn ial ▁collect ors ▁wel com ed ▁the ▁repr ints ▁and ▁hast ened ▁to ▁ac quire ▁them . ▁The ▁most