Melynn gave you census listings from 1850 and 1880. They show who was living in the household and how old they were at the time. I hope she e-mailed or called.
has marriages 1760 - 1900. It is touchy; sometimes it is up, some times down. I found these ARGO grooms in Piatt County:
ARGO, A PVANGUNDY, AMANDA J12/25/1861 00A/0026PIATT
ARGO, GEORGE FKNIGHT, FANNIE M06/24/1900 00B/0168 00000194 PIATT
ARGO, JOHNELLIS, SARAH09/05/1861 00A/0025PIATT
ARGO, JOHNMCKINLEY, MARTHA12/27/1864 00A/0033PIATT
ARGO, SOLOMONSKILLINGS, MARY (SEE SKILLINS)04/27/1865 00A/0034PIATT
ARGO, SOLOMONSKILLINS, MARY (SEE SKILLINGS)04/27/1865 00A/PIATT
and these brides:
JONES, HARRYARGO, CORA M12/16/1896 00B/0149 00002541 PIATT
OSBORN, ROBERTARGO, ESTHER01/21/1844 00A/0001PIATT
THOMSON, BENJAMIN WARGO, EVA M09/11/1890 00B/0106 00001679 PIATT
MCCLOUGHEN, CHRISTIAN (SEE MCCLUTHEN ARGO, EVELINE E03/19/1865 00A/0033PIATT
MCCLUTHEN, CHRISTIAN (SEE MCCLOUGHEN ARGO, EVELINE E03/19/1865 00A/0033PIATT
STOLLER, HIRAM A (SEE STOTTLER)ARGO, HANNAH10/10/1861 00A/0025PIATT
STOTTLER, HIRAM A (SEE STOLLER)ARGO, HANNAH10/10/1861 00A/0025PIATT
HARPER, WILLIAMARGO, HETTIE09/20/1899 00B/0166 00000098 PIATT
HENDRICKS, J WARGO, LUCINDA08/12/1885 00B/0073 00001002 PIATT
KENNEDY, WILLIAMARGO, MARY JANE03/20/1856 00A/0013PIATT
KANEDY, WILLIAMARGO, MOLLIE MAY07/26/1893 00B/0127 00002085 PIATT
COFFIN, JAMES BARGO, NANCY S11/13/1864 00A/0032PIATT
SPURIER, FRANCISARGO, REBECCA10/22/1846 00A/0002PIATT
HANNAH, JAMESARGO, SARAH10/04/1885 00B/0073 00001016 PIATT
Some may be cousins you didn't know about; some may be complete strangers. You might try searching yourself for specific names, using the link. If it is broken, try again after 10 - 15 minutes. It is under-funded, under-powered and very popular. You might try all counties, too, in case the happy couple eloped to a neighboring county. All of the ARGO brides or grooms in Illinois would over-load the server, so I limited my search to Piatt county. Play with it.
you have your choice of Solomon argos - born 1827, 1832 and 1837. The 1837 one is on the PRF, which is the LDS version of the World Family Tree CD's. He (the 1837 one)is married to Mary Skillings.
Cherie LOGAN, the PRF contributor, has a Charles Argo, b. 1873, the son of Solomon and Mary Skillings. When you go to the link above, find Solomon, then click on "Submission Search" and enter just the surname Argo.
has some tips for beginners.