Your best resource for pre-2060:
http://old.shadowrun4.com/resources/timeline.shtmlAlso, I'll go ahead and list the Primary Metaplots that mean something in 5th.
1: DUNKLEZAHN. Caps intentional. He became president of the UCAS and died, leaving a Will that changed everything. The Draco Foundation and DIMR are the two things closely related, but Wuxing wouldn't be listed in 5th as a megacorp without him, nor would NEONet. While many pieces of his Will have been dealt with inside the game, here's the whole thing:
http://www.shadowruntabletop.com/game-resources/dunkelzahns-will/2: Crash 2.0. Every character lived through this (11 years before 5th Edition's date of early 2075). It is directly involved with metaplot fears of AI and Technomancers. The metaplot on that goes back a few years, but reading the basics of "System Failure" could help.
3: Technomancers. Lots of folks are scared of 'em. "Emergence" is the start of that.
4: Dragon Civil War. It just happened, but many things had been a long time coming. Yet another thing tied into the Big D's death. "Clutch of Dragons" starts it, "Storm Front" ends some of it. For now.
5: Chicago and Bugs. This was HUGE, though many PCs will be too young to remember it. Everyone now knows about Insect Spirits because of this. The Spirits have been quiet since then inside the plot (Outside of Ares), but this was the biggest scare of the 2050s, and the ramifications are still felt. Pick up "Bug City" if you can, as anyone who is over 25 in-game will remember this. Any older (40+) Shadowrunner/Fixer/Mafioso probably had SOME dealing with the fallout.
All of these are pretty much puts to sink time/money into. Excluding a gap in metaplot between 2064 and 2070, there's well over 20 years of plots in Shadowrun. Some got dropped, some were just hooks, and some have been going for 20 years of game time. These are the ones that will get your team started in 2075 with a good history.
