When did the Power Stroke, Duramax, and Cummins get their start? One of these names is the first turbo diesel engine to be used in the larger full-size pickups, while the others replaced older, pre-existing diesel lines.
If we want to use the names we have for these engines now (and have had for a while), then the Cummins was the first one to come out. The 5.9L inline 6-cylinder B-series Cummins diesel was introduced in 1989 to trucks and buses, including the three-quarter-ton and larger Dodge pickups.
Next was the Power Stroke, beginning with the 7.3L, introduced in 1994. This V8 turbo diesel replaced the older 7.3L indirect injection (IDI) diesel. Both engines were produced by Navistar International; they had a pre-existing partnership with Ford. The new 7.3L was produced as the T444E (short for turbocharged, 444 cubic inches, 
electronically controlled) and rebadged as the Ford Power Stroke diesel. Ford's partnership with Navistar (previously International Harvester) continued until 2010 when Ford began producing its own Power Stroke engine, the 6.7L.
The Duramax is the newest of the current brands to be introduced. It started with the LB7 model name in the 2001 model year. General Motors teamed up with Isuzu, forming DMAX Ltd., to produce this new engine line. This engine replaced GM's old 6.5L IDI diesel used in the larger full-size pickups, making a vast improvement in engine technology.
Photos credited to SherwoodFord.ca, XtremeDiesel.com, and ShopDPS.com.