Today, the Ronald Reagan Presidential Foundation, the Manhattan Institute and The Wall Street Journal will host a morning seminar concerning the economic legacy of Ronald Reagan. The get-together couldn’t be timelier.

Reagan came into the White House facing an economy as troubled as ours—one that had even higher unemployment, catastrophic interest rates (18% for mortgages) and a stock market that in real terms had fallen 60% from its mid-1960s levels. When he left office eight years later, the U.S. had become an economic miracle: 18 million new jobs had been created; Silicon Valley had blossomed, becoming a global symbol for innovation; and the stock market was experiencing a bull run that, despite dramatic ups and downs, didn’t end until the turn of the 21st century, after the Dow had expanded 15-fold. The expansion of the U.S. economy exceeded the entire size of West Germany’s economy, then the world’s third-largest.

How did this happen? You could make the case that Reagan’s economic miracle had its origins at a Washington, D.C., restaurant in 1974. That December night, 34-year-old University of Chicago professor, Art Laffer, scribbled a single—and now legendary—curve on a cocktail napkin to illustrate to a group of President Ford’s advisers why a proposed plan to raise taxes would not increase government revenues. Mr. Laffer posited that deep cuts in existing tax rates would stimulate the economy and ultimately lead to far higher government revenues. Conversely, increase the tax burden and government receipts would fall below expectations because of a weaker economy.

Mr. Laffer’s curve headed off the tax boost, but the Ford people did not accept the conclusion that big reductions in tax rates were just what the anemic U.S. economy needed. However, when Reagan met with Mr. Laffer and other like-minded thinkers several years later, he quickly grasped the Laffer Curve’s fundamental message.

The concept that a free market unencumbered by barriers, government regulation and taxation will create the most growth-friendly economic environment was simple but radical. After taking the oath of office, Reagan went to work to convince the American people of the benefits of supply-side economics: lower taxes, less regulation, and less government spending, as well as a monetary policy focused on ridding us of the seemingly incurable disease of ever-rising inflation.

Reagan’s program was a resounding success. Its centerpiece was the Economic Recovery Tax Act of 1981, which dramatically cut income tax rates for everyone. He managed to pass the bill during his first eight months in office, with bipartisan support in a divided Congress.

President Reagan holds an oversized replica of an income tax form, June 13, 1985.

Critics howled that Reagan was being financially irresponsible, but the president pressed on. Once his cuts were fully phased-in and the hard fight against inflation was won, the economy took off like a rocket. Reagan’s achievements set up a great, long boom in the U.S. and the world that didn’t end until the economic crash in 2007. (Yes, there were periods of slower growth rates before that year, but none can be compared to the crash of 2007.)

At the same time, Reagan’s British counterpart, Prime Minister Margaret Thatcher, was accomplishing similar feats by taking an axe to Britain’s draconian tax system. Almost overnight, Britain went from being Europe’s economic weak link to being the continent’s most vibrant large economy.

Unfortunately, Reagan was unable to permanently rein in domestic spending and many of his reforms were undone by his successors. Washington politicians slid back into their bad habits, cluttering the tax code with new brackets, exemptions, deductions, phase-ins, carve-outs and special breaks for special interests. And the crucial importance of a strong dollar has been forgotten during the last decade, with terrible results. Today we are once again beset by a Carter-esque malaise, wherein we must accept abnormally high unemployment and the notion that printing more dollars is the way to recovery.

Yet Barack Obama’s 2011 State of the Union address was sprinkled with Reagan-like phrases, full of the 40th president’s trademark confidence. “The future is ours to win,” Mr. Obama said. “But to go there, we can’t just stand still.” He pledged to “knock down barriers that stand in the way of [American companies’] success.” We were told that the president had held meetings with Reagan administration officials, and that he’d even read Lou Cannon’s biography of Reagan during his winter vacation.

It’s true that both men came into office facing turbulent economies. But there the similarities end.

Reagan aggressively embraced free-market, supply-side principles that empowered the American people to rebuild and creatively expand our economy and standard of living. In contrast, the Obama administration has expanded the powers of government over us and our economy on a scale never before seen in peacetime American history. President Reagan understood, and fervently believed in, the American spirit of free enterprise. So far, President Obama hasn’t shown that he does.

Mr. Obama still has time to learn the real lessons of Reagan’s success. Will he?

Mr. Forbes, chairman and editor in chief of Forbes Media, is co-author of “How Capitalism Will Save Us: Why Free People and Free Markets Are the Best Answer in Today’s Economy” (Crown Business, 2009). He is also a trustee of the Ronald Reagan Presidential Foundation.