Dry ice is actually manufactured much the same way as described with the "fire extinguisher spraying into a bag" comment above. Liquid carbon dioxide, stored at 1073psi is sprayed into a porous bag, causing rapid evaporation to absorb enough heat that the rest of the CO2 freezes at -109°F (-78°C). The frozen carbon dioxide is gathered and then compressed by machines into blocks.

Dry ice was first made commercially in 1925 by the Prest-Air Devices Company in Long Island, NY to keep ice cream from melting. Those ice cream carts you see at theme parks are loaded with dry ice. I was "backstage" once and saw their huge liquid CO2 tanks.