The City of Greensboro North Carolina Library has a free Guilford County Marriage and Death Records, 1771-1899 Index with over 10,000 records including more than 20,000 individuals.
“The marriages are derived from three sources:
Marriage notices from the weekly newspaper, Greensboro-Patriot from 1826-99
Guilford County marriage bonds, 1771-1868
Guilford County marriage bonds abstracted in the book North & South Carolina Marriage-Records by William Clemens. Apparently, Clemens was in possession of some records that are otherwise unknown. His work must be taken as is, as its authenticity cannot be established.”