Float seems to have been originally designed to allow images and other sorts of things to move right, and allow the text to float around them. This is typical of figures in printed works. But designers found it was a way to put boxes next to each other, allowing more layout options. So now I'll quote Mark Twain just to fill things up.
The Mississippi is well worth reading about. It is not a commonplace river, but on the contrary is in all ways remarkable. Considering the Missouri its main branch, it is the longest river in the world—four thousand three hundred miles. It seems safe to say that it is also the crookedest river in the world, since in one part of its journey it uses up one thousand three hundred miles to cover the same ground that the crow would fly over in six hundred and seventy-five. It discharges three times as much water as the St. Lawrence, twenty-five times as much as the Rhine, and three hundred and thirty-eight times as much as the Thames. No other river has so vast a drainage-basin: it draws its water supply from twenty-eight States and Territories; from Delaware, on the Atlantic seaboard, and from all the country between that and Idaho on the Pacific slope—a spread of forty-five degrees of longitude. The Mississippi receives and carries to the Gulf water from fifty-four subordinate rivers that are navigable by steamboats, and from some hundreds that are navigable by flats and keels. The area of its drainage-basin is as great as the combined areas of England, Wales, Scotland, Ireland, France, Spain, Portugal, Germany, Austria, Italy, and Turkey; and almost all this wide region is fertile; the Mississippi valley, proper, is exceptionally so.
It is a remarkable river in this: that instead of widening toward its mouth, it grows narrower; grows narrower and deeper. From the junction of the Ohio to a point half way down to the sea, the width averages a mile in high water: thence to the sea the width steadily diminishes, until, at the ‘Passes,’ above the mouth, it is but little over half a mile. At the junction of the Ohio the Mississippi’s depth is eighty-seven feet; the depth increases gradually, reaching one hundred and twenty-nine just above the mouth.
Now, time for some boxes. The details are difficult to control, but note that they appear backwards. You can also do this with float:left, which fixes the order issue. Adjusting the exact position is difficult.
And this is pretty much what we did before. Using inline-block to arrange them.