I first put in 'McIlhagga' and got the nuclear family (part of my own) in Buffalo, Erie, New York in 1930, James and Jean both 32 (born 1898) and their son James aged 4. No new information there. I wondered where Ina (Alexandrina) McIlhagga was, but she appeared, also in Buffalo age 27, but at a different address, when I put in 'MacIlhagga'. It's always worth being creative with our surname!
That encouraged me to experiment with wild cards and first tried 'McElhag*'. I was hoping for at least one McElhago, but none! Sad, because I know there was an early one, and there is still one today. However there was one result from the 1840 Census, John McElhagin, of whom I have never heard. He was in New York, Ward 14. And there were the 13 people I hoped to find in Pensylvania. I thought they were all in Jamestown, but five were in Greenville, a town a few miles away, and like Jamestown also in Mercer County. I will list them next time and mention the new things I learned.