Over the past 18 years, I have gone through thousands of issues of Civil War era newspapers from throughout the state of Ohio and along the way have indexed quite a few of them. The focus of the indexes is to have a list of all the soldiers letters that saw print within- sometimes it takes a bit of digging to determine who the correspondents are but for the most part. Thus far, I have documented nearly 6,000 letters from 42 newspapers from around the state. As more than 210 different titles were printed during the war, about 20% of the issues have been indexed.
And don't think that the only thing you'll find within are letters from Ohioans- soldiers from all around the country wrote home to Ohio and it was not uncommon to see letters from states as diverse as Iowa or New York, along with letters from sailors in the blue and brown water navies.
You'll find that some of these are uploaded as Excel files and some as PDFs. The Excel files are newer and laid out such that I can use the data for a far larger Master file (not shared here). My apologies for any errors- enjoy!