Keep the Rust Belt clean!
Oh wait, you want an actual description? Oh fine, keep American manufacturing from taking the total dump it did OTL, and consequently somewhat depopulating the NE US.[1] Specifically:
Detroit must not at any point fall below a population of one million.
The NE must remain the population center of the US. No state outside can become a top 5 state (in terms of population)
There must, you know, be actual manufacturing going on. I don't really care what, so much (make it Rusty Silicon, for all I care), but it must be happening. In fact, the NE must remain the industrial center of the nation. No big Southern car factories.
Alright, go!
[1]For the purposes of this Challenge, 'NE US' means everything east of the Mississippi and north of Mason Dixon, including much of the usually-defined 'Midwest'. Importantly, this includes Ohio, Indiana, Illinois, and Michigan.