Easterseals will mark its 100th anniversary as a national organization this month, and it’s celebrating by illuminating landmarks across the country in Easterseals orange. In Greater Des Moines, the Financial Center at 666 Walnut St. in downtown Des Moines and the Altoona Water Tower in Altoona will be illuminated orange on the evening of April 21. Easterseals is the largest nonprofit health care organization in the United States, delivering services to and supporting more than 1.5 million people annually through a national network of 70 community-based affiliates, including Easterseals Iowa, which was established in 1926.