I saw a documentary about this once. At least I think it was a documentary. I was only 5, so I don't remember too well.

• Brand: Spreadshirt
• 100% cotton (heather gray and heather ice blue are 95% cotton /5% viscose. Heather blue & charcoal gray are 80% cotton/20% polyester. Heather burgundy is 60% cotton/40% polyester. Heather oatmeal is 99% cotton/1% viscose) | Fabric Weight: 4.42 oz (lightweight)
• Wide range of sizes from S-5XL
• Fairly produced, certified and triple audited.
• Double stitched, reinforced seams at shoulder, sleeve, collar and waist
• Optimized for beautiful brilliance across all printing methods
• Imported; processed and printed in the U.S.A.