#15261974 10c Robert Frost
$0.20- $32.00 #3189a1999 33c Celebrate the Century - 1970s: Earth Day
$1.95- $3.20 #11771961 4c Horace Greeley
$0.20- $39.00 #52842018 First-Class Forever Stamp - Flag Act of 1818
$0.30- $76.00 #15631975 10c Battle of Lexington and Concord
$0.20- $23.50 #11541960 4c Pony Express Centennial
$0.20- $28.00 #13741969 6c John Wesley Powell
$0.20- $22.00 #31341997 32c Literary Arts: Thornton Wilder
$0.20- $25.00 #22041986 22c Republic of Texas
$0.20- $52.00