Which of America's Presidents was the biggest spender?

There are a few major flaws in this measure. The first and most obvious is it doesn't take into account income. Clinton, for example, had a massive amount of tax revenue to play with so he could have spent more and still have increased the debt less.

The second issue is it doesn't take congress into account. Particularly the House whose Constitutional jobs is to control the purse strings. By that measure George W. Bush and Barack Obama come off quite a bit worse since both had clear majorities (I know that wasn't the case for any President since Reagan but my knowledge of congressional majorities is non-existent before that)

Finally there's the spill over effect. Reagan and Obama both walked into pretty big messes and the government always spends more in a financial downturn than it does in an upturn.

Congress spends, Presidents don't. Kind of a myth. Interesting data nonetheless.

These rankings assume that signing a law that creates a new entitlement that will entail large payoffs in future decades is "free". Being in office when those promises come due is profligate. In reality, we should be using accrual accounting, and book liabilities when they are incurred. This would more or less upend the rankings. (Mind you, this would be very difficult. The magnitude of the liabilities from PPACA are essentially incalculable at this point.)

And on a related note, the rankings also assumes that there is no lag in terms of fiscal policy. A president is responsible for everything done by the government from the moment he takes office to the moment he leaves. But of course, this is absurd. It may take a couple years to enact a new policy, and another couple of years for the effects to start showing up in government accounts. A big tax cut (or tax raise) might take a decade to work its way through the economy, once you include knock-on effects like changes in consumption or investment. More generally, it's trivially obvious that the deficit in any given year is not only (or even mainly) the result of policy enacted that year, or even during that administration (especially for the first year or two of an administration).

And as other commentators have noted, all of this is assuming that presidents even have control over the budget, taxation, and spending. They don't. At best they can sometimes convince Congress to give their ideas a respectful hearing, but rarely (if ever) will Congress simply enact a Presidential policy or budget. (And that's when the same party controls the White House and Congress. When they don't, they'll often enact the opposite policy just on general principle.)