The cyanotype process, also known as the blue print process was invented by Sir John Herschel in 1842 and is still performed today by many darkroom enthusiasts.
This is a process used first in the 1840's, developed by Sir John Herschel. He passed on information to his friend Anna Atkins.
©Anna Atkins. (British, 1797-1871). Polypodium Phegopteris. 1850-54. Cyanotype, 12 3/4 x 8 5/8" (32.4 x 22 cm). David H. McAlpin Fund
Alternative Photography would be a great place to read more about this process.