For what its worth, I was a freshman at Marian in 1977, the year Bimm started there, (I was not in band) and can tell you a little about the school then for your Marian 1970s-80s v. Limestone now debate. There was no football field - - home games were played at the local public high school. That was true until 1983. By then, Marian band was already attaining some success. The girls softball team's uniform was jeans and grey t-shirts. That was not true of schools we played. If rich parents were pouring resources into the school, it is surprising that it took 24 years to get a football field.
Now, Marian has a football field with lights, which is also the soccer field so band students practice in the parking lot when it is in use. I can tell you that the brand-new LW-North has far better facilities already than Marian has accumulated over the years. No one is saying Marian is a poor school, it is not, but most families I know that have kids there are blue collar, and in all cases both parents work. For many, Marian is a sacrifice but the local public high schools frankly have a poor reputation among many in the area so parents either send to Marian or move to another district. Look at the census data for Chicago Heights where Marian is. It is typical of the region. There are a few wealthy suburbs near Marian, many middle income ones and as many low income ones. The far south suburbs where Marian is are actually considered economically depressed.
All this is probably meaningless. Even if 1970s Marian were identical to Limestone now, the level of competition in the marching band world is undoubtedly higher and it is probably much harder to excel on limited resources than it was when Marian began its rise.
And a focus on who has the advantage of resources is ultimately toxic. My college friends send their kids to Carmel. The resources of Carmel are mind-boggling, and the gulf between Marian and Carmel (and I suspect Avon and LD Bell as well but dont know) is huge. That does not diminish their victories over Marian - - they earn them with hard work and I frankly couldnt care less how much money they have.