There is no mention of it in the CARMA Profile. The nearest I have for 158.760 is Beardstown in Cass County, and Atlanta over in Logan County. Also a couple FD's in Sangamon use it (Riverton and Williamsville).
Since Mason County is pretty much in the middle of these other users it is likely that you would hear traffic on it from at least one or two of them.
Like Gferg and others have said, that is the Logan County ESDA/Fire Department/Ambulance frequency. A couple of Mason County departments might have that in their radios to aid in interoperability with Logan County FDs (like New Holland and San Jose).