I've written about tracing Catholic churches before but wanted to add a few extra suggestions.
1. Identify all the Roman Catholic churches in the town.
a. Use their websites to find their foundation dates. It's not a perfect system, but it will help you identify what churches were in town at that time.
2. Make sure you read any and all history information available online. Sometimes the older churches will list their "mission" churches - even if those churches have since broken away.
3. Look at old maps. I recently discovered that a church that was supposedly founded in 1915 actually existed in 1860 as a mission church.
4. Call the diocese. A few have archives.