"Mapping" a fictional place

I'm in the process of writing my first novel and it's...daunting. I've never embarked on such a large work and it's taking much more time than I anticipated to figure out how anyone goes about getting started. Beyond simply considering, "what's the story and who are the characters?,"  and "Am I a writer who creates detailed outlines or shoots from the hip?," my professor has REALLY been stressing the importance of place/setting. Luckily, the novel I'm writing about a town on the southernmost tip of Illinois, (where the Ohio and Mississippi Rivers meet), originated by my fascination with that location, but Goldie Goldbloom has been pressing me to work with that in a much more detailed, thought-out way.

For example, Goldie has tasked me with making an uber-detailed map of my novel's landscape. Not just the simple geography, but also the more "micro" locations in the story where my characters spend time -- interiors of houses, backyards, fields, Main Streets, bridges, etc. Beyond creating maps, Goldie recommends that we find images of our setting and pin them up at our writing desk, and listen to music relevant to the story's timeline and setting,  to get even more engrossed in our stories. Full and complete immersion in story and place, in other words. These things might sound small, or obvious, but they're not, they're huge. After starting these practices, I've begun to feel much more oriented in my story. And I think readers can tell when the writer has a concrete sense of their setting; i.e., "authorial confidence." (Still, if anyone has any idea of what people in southern Illinois might've been listening to in the early 1970s and early 1990s, help a lady out.)