Marijuana.

For an example, look at the Canadian town of Smiths Falls. The Hershey's chocolate factory closed in 2008. It was a painful loss for the town, a major industry just gone.

Now "Tweed" a Marijuana growing company had taken over the space. They've been hiring at a tremendous rate, and even are planning an expansion to the factory, with even more jobs to come. Seriously, even the battered housing market is picking up again.

It's not an opportunity that will last forever, but the companies that capitalize on it have to opportunity to make a mint and a whole pile of happy workers in the process.

Wind turbine manufacturing. It takes ~500 workers to build a wind turbine. Close enough to the Midwest and East Coast (Ohio for inland, Michigan is on the Great Lakes if you want to ship out the Intercoastal for offshore wind on the East Coast) for transportation ease. Transition out anyone on the manufacturing line to PMs or turbine techs who want to get outside or relocate.

To power all of the US with wind alone would take ~4 million turbines, not to mention repowering existing wind farms over time. That’s a lot of manufacturing left to be done, and it isn’t going out of style anytime soon.