The Post Office Department issued seven groups of commemorative stamps between January 29 and February 12, 1940. These commemoratives stimulated tremendous interest in stamp collecting across the nation.
The second group, released between February 16 and February 24, 1940, celebrates American poets. Those honored in the series include Walt Whitman, James Whitcomb Riley, James Russell Lowell, Henry W. Longfellow, and John Greenleaf Whittier. Besides portraits of the poets, the stamps bear an image of the winged horse Pegasus, the steed which sprang from Medusa's neck when she was beheaded. Using an image of Pegasus on these five stamps represents the immortality of the poets' works and its timeless influence worldwide.