It's really encouraging to see the wide spread of career choices that have enabled people to out-earn the average American worker. Everyone thinks of doctors, lawyers, bankers, and engineers when they think of 100K+ salaries, but in many cases, it's simply a matter of choosing a career path that suits your own strengths, being flexible with job opportunities and locations, and being reasonably competent at your job. Some good ol' fashioned dumb luck and social connections are helpful as well (I have benefitted from all of the above).
I'm a forester. I did not go to forestry school because I thought I would end up earning $100K+. I just went because I enjoyed it. Turns out, there is tremendous demand for foresters who excel in mathematics/statistics and/or have experience in computer programming. Forestry is big business, and wherever there are large sums of money changing hands, there are people who are willing to pay good salaries to competent employees. I lucked into a job as an analyst with a big timber company (a job that I was not qualified for) a few years ago, simply because the job had been open for so long and there weren't any qualified candidates, and I had the gall to apply and was able to convince them that I could learn. They provided a juicy salary bump and on-the-job training. A couple years later, I moved into a senior analyst role at another company, with another nice salary bump. Et voila, suddenly I'm over $100K.
There are other roles in my industry (or any other industry) that offer similar or better salaries, but my interests/skill sets/disposition are simply not appropriate for those roles: procurement/sales, logistics, and management all affect the bottom line to such a degree that they command good wages. My older brother works for an auto parts distributor and makes >$100K as a logistics manager. My younger brother has a degree in agriculture and probably makes closer to $200K as a chemical sales rep. None of us has stereotypical "high-earning" degrees, but we all eventually made it into a career path that suits our own personal strengths, which I think is the most important key.