Do you know when and where William P. died?A copy of his death certificate should show the names of his parents.
1900 census Caddo Parish, LA, 533 Geasy or Geary St, Shreveport:
Buell, W.P., h, b Nov 1860, 39, M 16 yrs, b IA, IA, IA
" Daisy, w, b Dec 1867, 32, M 16 yrs, 3 ch, 3 lvg, b IA, IA, IA
" Walter, s, b Jun 1885, 14, b MO
" Dell, d, b Feb 1887, 13, b MO
" Thelma, d, b jan 1896, 4, b TX
[Occupation for W. P. looks like something for the railroad, but it is written over and not clear.It would account for the children being born in different places.]
1920 census Orleans Parish, LA, 441 St Charles St, New Orleans:
Buell, W.P., lodger, 61, md, b IA, Mich, PA
[Conductor, rail road]
I cannot find the rest of his family on the 1920 census.I don't have access to 1930 online at home.You can go to your local Family History Center, most are online now and they have a subscription to Ancestry.com, which you can use.Ancestry has an everyname index for the 1930 census you should be able to find members of the family on there.
Happy Hunting (^_^)