There's still method to that madness because art doesn't follow a prescribed path. For example, I recently combined Craftsman period details with a 200 year old molding style from Lowes new EverTrue line and a 100-year-old trimless window detail from the American 4-square period. And I could have made it all up from the ether, but knowing what's-what really helped me design it -- and build it -- better than guessing. WindsorOne.com is a great site for checking down four popular trim styles.

Pulling back a little to housing styles in general there's a nice timeline of which style was popular when at The House of Antique Hardware.

And while a timeline is handy for knowing when a style was hot, it's more useful to know some identifying details of the actual style -- Victorian, for example, is named for the massively detailed architectural style popular around the reign of Queen Victoria. Then there's Italianate (similar but different from Victorian,) Cape Cod (typically a 28x32 footprint with a 12-pitch roof popularized in America's first suburb Levittown, ironically built on Long Island, NY after WWII), Ranch or Rambler (a housing style popularized by Frank Lloyd Wright but only made tolerable as a resident by the existence of conditioned air; the house was affordable and gatewayed opening up vast tracks of populable land, like Florida and Arizona.)

Here's another thing this kind of high-fallutin' hoobbee-whatee opens up: your own opinion and -- dare I say it without becoming hopelessly lame?--your own sensibility.

For example, just because everybody says Wright is the bees-knees it's OK to not like him (gag.) One of my mentors loves Wright. I can't stand him, Wright that is. But the point is to GET what Wright is doing -- or TRYING to do--and how it's impacted the houses we work on (which is something I learned from my designer wife, who's a designer.)

You may not be called to frame an 18-in-12 turret on a Queen Anne or Shingle Style home or to set columns on a Greek Revival but when you meet with customers there's an unspoken expectation they have of you to know what kind of house you're standing in. By the way, if you're ever in Washington, DC visiting the National Building Museum will not be a waste of your time.
Now, you can stuff your tape measure in your overalls and stick a pencil behind your ear and bark, "Let's frame it!" and not really see all the implications of what you just said. Or you can have a working knowledge of the pieces and parts that go into building what they want -- and you can communicate that to them as well as build it into your bid so you can actually make money. Knowledge, esoteric or not, brings us closer to the art and science of how we make something work versus how we make something beautiful.

So here's your chance to take me to task: have my feet left the earth here? Do you expect your contractor to have an eye for proportion and architectural history? Do you want your trim guys to know the difference between Colonial and Craftsman trim details or do you just want them to nail the boards up and move on?