I was in Seattle this summer, and one of my big questions coming from the trip was why are the bridges so high?

I'm thinking of the two bridges that tower over Lake Union. 

1. Ship Canal Bridge.
2. Aurora Bridge.

Here's a section of Google Maps that highlights this area.

Delayed response

My friend Sally Anderson sent a message last night, a prodigious delayed response, saying she thought it was because the bridges got in the way of boat's masts, and they built them so high so the boats could pass underneath without having the bridges be drawbridges. 

At first I thought no way, these bridges are much higher than they would need to be to stay out of the way of boats, but then I found out that they had a bridge destroyed because a boat hit it, and the bridge had to be rebuilt. This happened in 1978, so it's not ancient history.

So maybe her theory is correct. 

Alternate theory

I offered an alternate theory.

I think they built the bridges so high because they could and it blew them away.

They looked at the bridges after they were built and said "Holy shit those bridges are way up there! We are very cool."

Because I think like an engineer. ;-)

PS: Brent Simmons, who lives in Seattle, adds: "We also have bridges so low they float on the water."