I've got a John McElduff and a Daniel McElduff in Illinois at Kaskaskia in the 1780s. John first shows up in 1778, at age 18, but could have been here earlier. Daniel may be his brother, because Spanish authorities (then just across the river in Missouri) later question some captives about the activities of the "Duff brothers." This Duff are sometimes listed as McElduff on the first reference in a document, but then just Duff for the second reference. Locals elected John and his likely father-in-law as justices of the peace in 1787. From the various documents it's clear that John's name was sometimes spelled John Michael Duff, John McDuff and John McElduff.