Hi Mark,
Creating 100,000 pages is definitely good for Search Engine because you have a lot more contents for them to crawl and have more chances your pages might show up on related keywords. However, the problem is do you have enough unique contents you can post on all those 100,000 pages. If you use similar content, I am afraid it will be duplicate contents. You may think changing up the town names will be enough but it might be risky.
If you can create 100,000 unique contents, Sure go ahead. If not, don't take the risk of duplicate contents.