I was on a long trip across South Dakota and less than 200 miles into it, the ride gets shaky and starts bucking. I checked the tires, thinking one was deflated or a wheel weight fell off. Nope. Kept driving and it would keep bouncing and pulling back.
Then down the road something in the engine banged and it got this really loud tractor cackle. I managed to drive into the next town with no problems but what's making this sound?

It was also 10 degrees outside, the engine was getting a bit hot, and this could be my imagination, but the dipstick shows I may have burned about a pint of oil within two miles.

 

like a knocking sound?

if you heard a bang and then knocking that only means one thing

a rod saw the outside world

 

It still sounds like a tractor though. It was bucking and bogging in gear on the highway so I thought maybe it's just ball joints at first. Now it sounds like there's a big straight pipe exhaust with no power.

 

Reads like a clogged exhaust, the loss of power and bogging, then exhaust connection or weak point opened to relieve some of the pressure.

Could be the EGR pipe opened as well, that is part of the exhaust system, and it also helps cool the engine when under load, i.e. driving.
Loss of EGR system would also cause pinging which you probably wouldn't hear over exhaust noise but pinging causes loss of power and piston damage if it occurs long enough

Loss of oil wouldn't be part of the above.