Thanks for the kind words. I hope all the census information can help people out.
I have begun gathering the Rigsby entries from the 1900 and 1910 censuses. Fortunately, your Lewis is among the ones I've already found. Here he is:
1910 census Gallatin Co IL p16a Louis P Rigsby 67 TN/US/US wife Mary H 41 IL/IL/IL son Henry 22 IL son Bengim? 19 IL son Blaine 17 IL son Ray 15 IL sson John E Vicray? 21 sson Charles A Vicray? 20 sson Guay? Vicray? 19 sdau Ettily? Vicray? 13
I'm guessing "Bengim" is "Benjamin". I couldn't read very well the last name of the step- children. There is a good chance it should be Vickery. Note that the ages of Mary H's children imply that she was married to Lewis after Ray was born.
1900 census Union Co KY p1a Louis? Rigsby 55 1844-11 TN/TN/TN son Henry 13 1886-06 KY/TN/TN son Ben 10 1889-07 KY son Blaine 8 1891-10 KY son Rhea? 6 1893-12 KY
Note that Lewis has no wife in 1900. It certainly appears that Mary H was his third wife, that she was previously married, and that she was not the mother of the 4 sons. Since you know Lewis married Mary Chambers in 1884, she must be the mother of Henry. However, if Mary died in early 1889, she can't be the mother of Ben, Blaine, and Ray. I wonder if Lewis had yet another wife between the Marys. How certain are you of the 1889 death date for Mary Chambers? Also note that the children are shown as born in KY, but in 1910 they are shown born in IL. I think KY is right.
If we had the 1890 census, we should find Lewis as a widower, with 2 young sons. It would be interesting to see if he was married again (or still).
Stepping back to 1880, we should be able to find Lewis age 36-ish. The only possibility, as you saw, is Lewis age 34 in Allen Co KY:
1880 census Allen Co KY p243c Lewis Rigsby 34 TN/TN/TN wife N J 29 KY/NC/KY son Andrew 14 KY son J Henry 7 KY nie M J Pearson 5 KY/KY/TN
In 1870, there is again only one possible match, this time in DeKalb Co TN:
1870 census DeKalb Co TN p182 Lewis T? Rigsby 24 TN Nancy J 19 TN Andrew 4 KY Lavina? 40 TN Caroline 16 TN
Apparently that middle initial, which was hard to read, should be "P". His wife is Nancy J, and son Andrew is 4, so this must be the same as the 1880 Allen Co KY family. Lavina is Lewis' mother. Her age should be 48. I'm not sure who Caroline is.
In DeKalb Co TN in 1860 is this family:
p130 Kennedy Rigsby 38 Lavina A 38 Lewis P 16 Andrew M 14 Elizabeth A 11 Charlotte C 8 Nancy A Maynord 84widow
This is Kennedy/Canada Jr Rigsby and his wife Lavina Maynard. Nancy Maynard is Lavina's mother.
And here's Kennedy/Canada Jr in 1850:
1850 census White Co TN p59 Canada Rigsby 29 TN Lavinia 28 TN Lewis 6 TN Andrew M 5 TN Elizabeth A 2 TN Gibson Maner 80 VA Lucy Sullivan 15 TN
Gibson Maynard is Lavina's father. I don't know yet how Lucy Sullivan fits in.
So your Lewis P Rigsby was a son of Kennedy/Canada II Rigsby + Lavina Maynard. Note that White Co is a ways north of Chattanooga. Kennedy/Canada was in White Co in 1840 as well, so it doesn't look too likely that your Lewis was born in Chattanooga.
Kennedy's father was Canada Rigsby born c1788 Mecklenburg Co NC, died c1849 DeKalb Co TN. Canada married Mary "Polly" Lewis d/o William Lewis.
Canada's father was Thomas Rigsby born c1760, who lived in Mecklenburg Co NC in 1790. Thomas died between 1830 and 1840 in Warren Co TN. I don't yet know the name of Thomas' wife or parents.