I know several people who have had antibody tests because they had a fairly intense respiratory illness back in February and March, but they all tested negative. It was probably the flu or something else.
Here are the stats for the Peoria tri-county area, and they are relatively low compared with Chicago (stats are updated daily)-
https://www.pcchd.org/289/COVID-19-Coronavirus
There are fewer than 250 positive cases in all 3 counties, and that is despite much wider testing which was predicted by some to detect a lot more cases. Only a small number of those were hospitalized. And unfortunately, there have been 6 deaths in Peoria County, 3 in Tazewell, and 2 in Woodford.
From studies done in a couple different parts of the county, there are probably more people who have had mild forms of the Covid-19 disease, and may have antibodies and don't realize it. But overall, this area, and nearly all of downstate Illinois have had very few number of cases. There are even a couple Illinois counties that have had zero cases, and many more than have had fewer than 5-
Illinois stats by county (hold cursor over each county for total cases)
https://coronavirus.illinois.gov/s/
Yet even those counties with no cases are subjected to the extreme restrictions put in place by the governor.