Coinciding with the 50th anniversary of Earth Day, the Postal Service issues a stamp featuring a playful painting of the planet, with small green lines surrounding Earth and hand-lettered text. Environmental groups have sought to make Earth Day into a day of action to change human behavior and provoke policy changes. Walt Kelly created an anti-pollution poster featuring his comic strip character Pogo with the quotation “We have met the enemy and he is us” to promote the 1970 Earth Day. Preceded by various environmental-themed stamps, the first USPS Earth Day stamps were not issued until 1995. Art director Antonio Alcalá was the stamp artist and designer. Ricky Altizer was the typographer.