History question: I-80 alignment in Salt Lake City

[Sub-Urbanite]

Totally random history question that's popped in my mind: Does anyone know why I-80 was aligned the way it was through the Salt Lake Valley?

Specifically:

- Given that the general practice of the time was to route interstates through city centers, why did Utah instead opt to align I-80 nearly two miles south?
- That's especially true given that the westside alignment of I-80 joins I-15 right about where you'd expect Eisenhower-era planners to cut an east-west freeway through downtown.
- On the other side of that, why go with the northern alignment west of I-15 vs. the UT 201 alignment?

It's all somewhat odd. Looking forward to what the historians have to say.

[NE2]

Perhaps the initial planned alignment was placed along US 40 and nobody saw any reason to change this. US 40 used East 2100 South and West North Temple.
http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~212156~5500255:Various-Regions-and-Cities-in-Utah-

[Sub-Urbanite]

That would be a simple, logical explanation!

But in that era, it was also logical to take out half your downtown to build a freeway.

Perhaps the initial planned alignment was placed along US 40 and nobody saw any reason to change this. US 40 used East 2100 South and West North Temple.
http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~212156~5500255:Various-Regions-and-Cities-in-Utah-

[coatimundi]

Obviously freeways were much easier to push through urban areas in the middle 20th century than they are today, but they were still much more expensive to build in those areas than on undeveloped land, so planners often still chose the path of least resistance. Additionally, I-80 follows Parleys Creek out of the mountains, and topography likely makes it easier to stay on it into the valley.
Also, Sugar House Park, which the freeway abuts, was the site of a state prison (link) that was closed just before the freeway was built, giving the state some easy and free land to use.

I also wonder if I-80W-I-15S & I-15N-I-80E traffic was taken into consideration with respect to the lack of a bypass. I-215 east wasn't built until several years later, and I wonder if there was already an understanding that it would take time to get that part of the road built.  Keeping I-80 going due east-west out of Parleys Canyon would keep traffic that tried to avoid that northern jog off of the side streets in the south valley.
Just a theory.