Customs and Border Protection continue to stay on the offensive in the safety and security of the seaports. The rapid increase in the growth of containers will continue to be an ever-evolving challenge. However, through training and determination, this goal will be accomplished with innovative strategies, such as the Container Security Initiative (CSI) launched in 2002 and the Customs Trade Partnership Against Terrorism (C-TPAP); in addition, increased technology of nonintrusive imaging and radiation detection equipment has been deployed, as well as the ongoing relationship building between the public and private sector. Containers were first used by railroads in the United States in the 1920s. In the 1950s, steamship lines in the United States first began to use containers to ship goods. Soon afterwards, vessels were specifically designed and built to carry containers throughout the world. In the past decade, this growth of containers entering the United States has tripled in volume from 137 million to 417 million TEUs (20ft equivalent units). This increased growth in trade which has increased the threat of terrorism continues to provide Customs and Border Protection with a daunting challenge in security at the ports of entry.