While doing my due diligence for a novel I want to write, I came up on something. If I know that a mail drop location is at a certain address, now, in 2015, but want to know if it was there in 1988 for example, how would you go about researching this? Even if the company exists, it might not have had the property lease in that specific year. If I were to do a more open-ended approach, and want to know where in a city like Miami there's a mail drop, anywhere will do, how do you research it? Does it even strictly matter if it's not a monument, a public library, museum, or famous local joint etc and the specific address isn't critical to the plot?