Founded in 1937, The Society of the Plastics Industry, Inc., is the trade association representing one of the largest manufacturing industries in the United States. SPI's members represent the entire plastics industry supply chain, including processors, machinery and equipment manufacturers and raw materials suppliers. The U.S. plastics industry employs 1.4 million workers and provides more than $310 billion in annual shipments.

The SPI introduced its Resin identification coding system in 1988 at the urging of recyclers around the country. This system was introduced to make separation of the many similar-appearing plastic resin types easier for recycling centers across the country. There was no federal legislation or program to mandate these symbols, though many states have now adopted legislation that mandate its use.