Why does it overheat
I've taken the thermostat out & still I can't go more than a half mile before my car overheats
check to make sure that the cooling fans come on. Since it overheats so rapidly I’d be looking into the possibility that it is a water pump issue. Check for leaks etc. Let us know the exact year and engine size. You know it overheats because it is steaming etc. or are you going by the gauge.
In addition to oldturkey03 comments, just wondering if this engine has been running with a bad coolant blend.
Running the engine using primarily tap water and/or not enough coolant/antifreeze in the mix has the engine running hotter and allows rust to form and deposit throughout the system, and potentially obstructing passages and the coolant flow from circulating as designed.
Using different coolant/antifreeze formulations (like the green mix and the orange mix, for example) can result in a thickish goo forming in the coolant system - not good.
If either of these applies to your situation you would want to perform a series of engine coolant flushing exercises to try and clear the passages, etc., then recharge the system with the right mix of the right type of coolant (and don’t forget to “burp” the system when you’re done.