Architecture is more than just buildings.
Certainly, the first thing most people think about is the way a building looks: steel and glass, colonial revival, Tuscan, Beaux Arts.
But when we consider the history of the Valley through its architecture, we're talking about the entire built environment, which includes not just the edifices, but the streets, the canals - even the storm drains and the power lines.
History is an act of the imagination.
You look around the Valley today and you see office buildings, tract housing, paved streets, power lines and fast food.
But try to imagine what the land looked like before. Picture, if you can, a flat Salt River Valley raspy with greasewood, saguaro and ocotillo as far as the eye can see. There are mountains in all four directions and a flowing river in the middle. The flats by the water's side are choked with reeds and grasses.
Before the First World War, the Valley was a tiny group of villages. It was a day's wagon trip to go from Tempe to Phoenix to do to your shopping. The northern limit of Phoenix was Van Buren Street. Scottsdale barely existed.
After the Second World War, the Valley exploded into the sprawling metropolis we have today, spread 60 miles east to west and 45 miles north to south.
Postwar America lived under a mushroom cloud, an explosion that ended a hot war and heralded the beginning of a cold one.
But in Phoenix, the explosion was more immediate. It was real estate.
There is a type of drawing where the pencil point never leaves the paper, and a long, elaborate line, full of circles and curlicues, outlines a caricature or landscape. It is not an easy style to pull off, but when it's well done, it is admired not only for the image, but for the technique.
History is one of those drawings. The pencil point is the moving present, and the past is not merely the line on the paper, but the image it makes: something comprehensible and coherent.