Webb City is a suburb of Joplin in Jasper County Missouri which has a history of early lead and zinc mining:http://www.historicjoplin.org/?tag=jasper-county-mininghttp://www.historicjoplin.org/?tag=mining-in-jasper-county-m...
Perhaps the name is Tholborn, misread or misspelled?
1900 Webb City census:
Walter Tholborn 1846 England, salesman, immigrated 1852
Hila C. " 1851 Iowa, wife
Joseph O. " 1874 Mo
W. Harry " 1883 " laborer, zinc mine
W. Harry Tholborn's death certificate:http://www.sos.mo.gov/images/archives/deathcerts/1946/1946_0...