Image: Hijacked United Airlines Flight 175 from Boston crashes into the south tower of the World Trade Center © Spencer Platt, Getty Images

Sept. 11, 2001, was a one-of-a-kind moment for the nation's psyche. The terrorist attacks killed nearly 3,000 people, rained down fear and grief on countless others and launched the nation into two wars.

But was that day similarly devastating for the financial world?

At first glance, it seems the answer is yes. On Sept. 17, 2001 -- the emotional date that the New York Stock Exchange reopened amid soldiers, police and Wall Streeters wearing air masks on the smoky streets of lower Manhattan -- the Dow Jones Industrial Average ($INDU)lost 684 points, at the time the largest single-day point loss on record.

Yet with a decade of hindsight, 9/11 can be seen as but one of a half-dozen financial dominoes that have fallen for the U.S. economy during a long boom-and-bust cycle -- from the 1998 collapse of the hedge fund Long-Term Capital Management, to the demise of Lehman Brothers amid the 2008 financial crisis, to more recent events, including the ongoing European sovereign-debt crisis and the downgrade of the United States' AAA credit rating.

"Nine-eleven was a shock, that we were in a new world where America was no longer as safe as it was," said William Silber, a professor and historian at New York University's Stern School of Business.

For a short time, the attacks and the fear and uncertainty they spawned were a classic case of perception versus reality -- the situation looked worse than it was.

Events like 9/11 create "sudden substantial revisions in expectations about future economic and financial variables," Christopher J. Neely concluded in his 2004 study "The Federal Reserve Responds to Crises: September 11th Was Not the First," (.pdf file).

And while 9/11, like other financial episodes of recent years, is symptomatic of the age of leverage on Wall Street, it differs in one key way: It is a classic example of an external shock, like Pearl Harbor or the 1973-74 oil embargo. It was not a self-inflicted wound, such as the subprime crisis, or a cyclical downturn, such as the 2001 and 2008 recessions.

"The difference is whether the shock has a temporary liquidity impact versus an underlying credit impact. Nine-eleven didn't necessarily go to the underlying creditworthiness of the institutions," said Silber, who chronicled the monetary crisis surrounding World War I in "When Washington Shut Down Wall Street."

Adds Silber, "It goes to (show) how easily the central bank can counteract (a crisis) and can stabilize the system."

Thanks largely to leverage, the last dozen years have been a timeline of boom and bust, of a financial-services-dominated economy out of control and a central bank compounding the problem with cheap money and other instruments of interventionist monetary policy.

"It sounds a whole lot like the economy during and after the Civil War -- one step forward and two steps back," says Charles Geisst, a professor of finance at Manhattan College.

Silber compares the modern period to the stock market crashes of 1929 and the 1930s. "There was not just one event but a series of events," he said.