Content affects SEO in a huge variety of ways, including the Google Local Search Results, aka map results.
Perhaps the biggest factor of Google Local Search results in 2016 is organic rankings. You can perform practically any search in any city and the local results practically mirror the organic results. Of course, there are other factors but this is very obviously the most apparent.
Different search queries trigger different local results
Here’s an example: Not all injury lawyers in Dallas have a page dedicated to “motorcycle accidents”. However, the attorneys that do have a page (which ranks) for this search query get the benefit of showing up in a local result as seen here:
In almost every type of business, more content can trigger more local 3 packs. Massage therapists and day spas can have a page dedicated to “sauna” if they offer it. Restaurants can have a page dedicated to “pizza” if they serve it, and real estate brokers whose content ranks for terms such as “real estate agent”, “real estate broker”, “Realtor”, or “realty”.
Content which affects local search results
Having a variety of pages which rank for certain search queries affect local search results.
The pages which rank organically may simply be similar pages, unique pages dedicated to said search term, or pages which rank organically due to long tail search terms.