The first Japanese immigrants arrived in the United States on May 7, 1843. The transcontinental railroad, whose completion would have been impossible without the hard work and sacrifice of many Chinese laborers, was finished on May 10, 1869. These important anniversaries led President Jimmy Carter to designate the first Asian Pacific Heritage Week in 1978. In 1990, Congress voted to designate the entire month of May as Asian Pacific Heritage Month.
Meanwhile, if you're near D.C. anytime soon, make sure to visit Smithsonian's Freer and Sackler gallieries, which are dedicated to Asian art.