Here's some info on National Poetry Month from Poets.org
National Poetry Month was established by the Academy of American Poets as a month-long, national celebration of poetry. The concept was to increase the attention paid-by individuals and the media—to the art of poetry, to living poets, to our poetic heritage, and to poetry books and magazines. In the end, we hoped to achieve an increase in the visibility, presence, and accessibility of poetry in our culture. National Poetry Month has been successful beyond all anticipation and has grown over the years into the largest literary celebration in the world.
The Academy of American Poets has led this initiative from its inception in 1996 and along the way has enlisted a variety of government agencies and officials, educational leaders, publishers, sponsors, poets, and arts organizations to help.
April. Every year since 1996.
With input from booksellers, librarians, poets, and teachers, the Academy chose a month during the school year so that schools and students could participate fully. February is Black History Month and March is Women's History Month, so April seemed a logical choice. Also, there are many wonderful poetic references to April:
T. S. Eliot wrote, "April is the cruelest month." It is our hope that National Poetry Month lessens that effect.
On a lighter note, Chaucer wrote:
Whan that April with his showres soote
The droughte of March hath perced to the roote,
And bathed every veine in swich licour,
Of which vertu engendred is the flowr
Finally, Edna St. Vincent Millay asked, "To what purpose, April, do you return again?" For National Poetry Month, of course