They are the unsung heroes of the U.S. economy. Companies with annual revenue between $50 million and $2 billion. They're lithe enough to maneuver, but big enough to have a broad impact. They employ 35 million people--about one in four U.S. workers. They deliver nearly 40 percent of the country's economic vitality. They are America's midsize companies, and it's time they are recognized. Looking at 14 different points of comparison, Inc. is for the first time ranking management excellence across the middle market--because thriving companies tend to be well run. In aggregate, the 250 public and private companies, identified here with the help of Inc. chief data scientist Arnobio Morelix and Shango Labs, created more than 540,000 jobs and generated more than $140 billion in annual revenue. The results are the following kernels of hard-won wisdom and sage advice--on everything from hiring and retaining top talent to putting out fires and managing amid a crisis. Because it's one thing to sing the praises of these heroes of the U.S. economy. It's a far better thing to learn from them.