The US National Debt is the result of the US government spending more money than it takes in: overspending.

The current US National Debt is the result of overspending by the US government for the last 100+ years.

Politicians are able to confuse many people by talking about an annual "budget deficit" which refers to the amount of money authorized for a given year. The problem seems to be that the executive branch spends what it wants, regardless of the budget.

Don't be fooled by the tricks. In a year when the US government takes in less than it spends, the US National Debt goes up. In a year when the US government takes in more money than it spends (rare), the National Debt goes down.

Here the raw numbers from 1900 on. No spin, no BS, no "blame game". Here are "just the facts, m'am":

                                                    raw data: US National Debt 1900-2005

Note the National Debt change between 1959 and 1960. Also note the change between 1999 and 2000.

Another interesting figure is the revenue that came into the federal government in 1995-2005. The annual debt will change equally do to lower revenue or increased spending. Usually it is from a spending increase, other times a drop in revenue (rare).