I’m trying to get handle on why so many US stations have cooled since 1900. So I thought I would zoom into an area bounded by Latitude 38 and Latitude 43.999 and Longitude 92W and 83W which is roughly centered on Gary Indiana. I am not an expert on that region, but it seems to me that a lot of the warming stations are centered in those circles Google Maps shows for cities. I suspect that UHI is the cause of much of the warming and the reason some stations are cooling is because they have less UHI.
Of the 181 stations on this map, 93 are cooling and 88 are warming.
The mean of the warming stations is 0.061C/decade.
The mean of the cooling station is -0.051C/decade.
And the overall mean is a minuscule 0.0036C/decade.
sunshine hours 
The most obvious reason for cooling, or less sunshine hours, is the effect of pollution and steam from coal power stations, which are the main source of energy in Indiana. While the CO2 ultimately promotes global warming, locally you get cooling, due to atmospheric pollution and to extra clouds.
I cannot see the pattern you are implying – if anything, a lot of the warming stations are out past Fort Wayne and in places no one lives.
Some of my other posts try and break things down to the county level.
But I was interested more in the fact that there is a cooling trend from 110 years in the past.
But I’ve also thought about the opposite situation. If, as you suggest, cooling is caused by dirtier air, then warming could be caused by cleaner air. And I return to that theme in other posts.