At loooooooooong last, I've found my 3rd-great-grandmother on a census prior to 1880. Cornelia McCLELLAN appears with her parents and two younger brothers in the 1870 U.S. Federal Census in New Haven Village, Armada Township, Macomb County, Michigan. It took some tricky searches to find them, as her father is enumerated as "Levy MACLALLEN." Cornelia herself was indexed as "Amelia" and her mother as "Charissa." Thank goodness for Ancestry's "correct an error" feature for census records! I sent in the correct and alternate spellings for all three.
I still can't find these people in 1860, although I have done many rigorous searches late last night and early this morning. A search in the 1880 census for the other family members (I already had Cornelia's enumeration for that one), gave me a possibility for Levi in Detroit, with a possible second wife (Mary C.), new son (Ira, age 10), and step-son (George, age 14). This Levi matches in approximate birth year, birth place, and occupation (carpenter) my Levi of 1870. Clarissa and Edmund (probably both deceased) are nowhere to be found. There are several possibilities for William in the state.
The 1900 census does not enumerate Levi, or at least, I haven't found him. I did find an Ira whose birth year and birthplace match, residing in Washington Twp., Macomb County. His occupation is a (stove/steve/? joiner). Joiners and carpenters are pretty much the same occupation, and if this Ira is Levi's son, above, it's possible he learned the trade from his father.
Any of you who've done this for a while understand what I'm talking about when I say there are certain families that you can trace all the way back to the ship, with plenty of supporting documents; and then there are those that make you want to bang your head on the wall (like this family)! However frustrating the latter are, they are the ones I learn from the most. I learn to use alternate spellings, think creatively, analyze, organize my information, and simply to persevere. And these are the ones that make genealogy so interesting and rewarding!