Nancy, I don't know whether anyone has gotten back to you by now or not, but births were not registered in Pettis County until 1867. You can find them at http://www.sos.mo.gov in their archives. And, yes, there was a Pettis County, at least as far back as 1860. I could find No Callahans or Callaghans in any Pettis County town for the 1860, 1870 or 1880 US census. Maybe James worked for the railroad? Those workers moved around a lot. If I can help you further, please let me know. Carolee