In 1870 U. S. Census, there is a Robert Taylor, c.1816 born in Australia, living as a farmer at Johnson, Knox County, Ind. with wife Nancy, c.1831 born in Indiana and possibly step-daughter Isadore West, c.1854 born in Indiana.
This is the only US Census entry I could find but the information does not match
the Illinois Muster Roll which has his birth year as c.1847.
The muster roll also lists him as a farmer, five feet, 11 inches tall, dark hair and brown eyes.