Hulton Archive / Getty President Franklin Roosevelt

Look how far we've come. That is the aim of the 100-day retrospective, to assess our new leaders after they've had enough time to take action but before they've solidified their legacy. And although it seems like an arbitrary measure  if something happens on the 101st day, is it somehow less important?  Presidents can get a surprising amount done in their first three-and-some-odd months. (See behind-the-scenes pictures of Obama.)

The 100-day timeline can be traced back to Napoleon Bonaparte, because that's how long it took him to return from exile, reinstate himself as ruler of France and wage war against the English and Prussian armies before his final defeat at the Battle of Waterloo. (It actually took 111 days, but we'll give him a mulligan.) Napoleon reclaimed power in 1815, however; Americans didn't start assessing their Presidents in 100-day increments until Franklin Delano Roosevelt came along more than a century later.

Roosevelt was a presidential overachiever  and his swift, take-charge method of governing was exactly what an ailing, Depression-weary nation needed in 1933. After delivering one of the most famous Inaugural speeches in presidential history  does the phrase "The only thing we have to fear is fear itself" sound familiar?  Roosevelt had been in office barely 24 hours when he declared a four-day bank holiday and drafted the Emergency Banking Act, which helped calm a financial panic that was quickly spiraling out of control. By the time he hit the 100-day mark, Roosevelt had instituted the "fireside chat" tradition, called Congress into a three-month-long special session and passed 15 pieces of major legislation  the beginning of what would come to be known as the New Deal  which created everything from the Tennessee Valley Authority to the Federal Deposit Insurance Corporation. With farm credits, federal works projects and new financial regulations in place, the U.S. of June 1933 was a substantially different place from that of 100 days earlier. (See a special report on Obama's first 100 days.)

Roosevelt was enormously popular (hence the fourth term), and later administrations have tried to associate themselves with his early success. "Jerk out every damn little bill you can," President Lyndon Johnson reportedly commanded his strategist Larry O'Brien in 1965. "Put out that propaganda ... that [we've] done more than they did in Roosevelt's hundred days." Propaganda or not, Johnson actually had a very effective 100-day run: after being sworn in as Kennedy's sudden and unexpected successor, he advanced the passage of the Civil Rights Bill, established the Warren Commission to investigate J.F.K.'s assassination and got into a political fight with Fidel Castro over the water supply at Guantánamo Bay.

Ronald Reagan beat Roosevelt's 24-hour effectiveness record when the 52 U.S. diplomats held hostage by Iranian militants for 444 days were released on Jan. 20, 1981  the same day on which he took office. Reagan's next 99 days were a bit more subdued, but they still featured $41.4 billion in proposed budget cuts, large tax breaks, the formation of an oversight council to combat government corruption and a dramatic assassination attempt. When John Hinckley Jr. shot Reagan on March 30, 1981, the President's approval rating jumped as high as 68%, but by the 100-day mark, it had settled back down to about 51%. (Jimmy Carter had clocked in at 64% four years earlier.)

President Bill Clinton spent his first 100 days bouncing between a series of blunders: unsuccessful Attorney General nominations, Hillary Clinton's failed health-care reform, "Don't Ask, Don't Tell" and the botched Branch Davidian raid in Waco, Texas. President George W. Bush presented a $1.96 trillion budget plan to Congress, created an Office of Faith-Based and Community Initiatives and halted federal funding for international organizations that offered family-planning services.

Barack Obama may be the first President to actually rival Roosevelt in terms of the sheer number of changes. Only 6% into his 1,461-day term, Obama has already signed a $700 billion stimulus bill, tried to bail out Detroit, lifted a ban on stem-cell research, planned a withdrawal from Iraq, reached out to Cuba and authorized the release of Bush-era torture memos. Oh, and he got a dog. Roosevelt didn't adopt his beloved Fala until the end of his second term.

One hundred days is a long time, and although the presidential progress report serves as a general gauge for the direction of the country, most administrations don't achieve (or suffer) their greatest milestones until later. The 9/11 terrorist attacks, the Lewinsky scandal, Truman's decision to drop the atomic bomb  they all fell outside the 100-day mark. Kennedy's deft handling of the Cuban missile crisis outweighed a number of disasters (Bay of Pigs) and minor setbacks (Russia's first-man-in-space triumph) that marked his first 100 days. And while Nixon's presidency started off smoothly, he rejected the 100-days judgment, telling the New York Times in 1969 that he preferred to be judged over the long term. Guess we know how well that turned out.

See pictures of Presidents and their dogs.

See Mark Halperin's report card for the Obama Administration.