With Warren Buffett’s purchase of Burlington Northern (BNI), there’s one less trans-continental railroad in North America. And nobody is going to build another one anytime soon. Actually make that ever.

 Canadian National Railway (CNI) generates the highest operating margins among North American railroads. Its operating ratio (that’s the ratio of operating expenses to revenue) has climbed to 63.6% from 89.9% over the last decade, according to Morningstar, and the company’s 10-year free-cash flow is more than 13% of revenue.