The William Ashcraft I found is not the right one. His father appears to be Uriah Ashcraft of Harrison Co, KY. Here's your William Ashcraft living next door to his parents, Samuel and Caroline Ashcraft in Grant Co, KY.
1880 Federal census: Census Place Grant Co, Kentucky Family History Library Film1254415 NA Film NumberT9-0415 Page Number4A
NameRelation Marital Status Gender Race Age Birthplace Occupation Father's Birthplace Mother's Birthplace Samuel H. ASHCRAFTSelfMMaleW54KYFarmerKYKY Caroline A. ASHCRAFTWifeMFemaleW49KYKeeping HouseKYKY David W. ASHCRAFTSonSMaleW13KYAt HomeKYKY Eliza A. ASHCRAFTDauSFemaleW10KYAt SchoolKYKY Margeret AYDLESTLEOtherDFemaleW45KYLiving With FamilyNCKY
NameRelation Marital Status Gender Race Age Birthplace Occupation Father's Birthplace Mother's Birthplace William A. ASHCRAFTSelfMMaleW32KYFarmer & MechanicKYKY Sallie A. ASHCRAFTWifeMFemaleW26KYKeeping HouseKYKY Stephen R. ASHCRAFTSonSMaleW1KYAt HomeKYKY
Here's William A. living with his parents in 1860 Grant Co, KY:
1860 United States Federal Census Williamstown, Grant Co, Kentucky, p. 151 Household Members: Name Age Samuel H Ashcraft 34m farmer $700r $250p KY Caroline Ashcraft 29f KY William A Ashcraft 10m KY Samuel M Ashcraft 8m KY Mary E Ashcraft 6f KY John J Ashcraft 4m KY Stephen R Ashcraft 1 m KY
1900 United States Federal Census Short Creek, Pendleton, Kentucky, p. 5a Household Members: Name Age Samuel H Ashcroft 74head w m Nov 1825 md 42y KY KY KY farmer Caroline Ashcroft 69wife w f Dec? 1830 12ch 8liv KY KY NC Lounette Ashcroft 18grdau w f Nov 1881 KY KY KY
I don't know how I missed these listing when I looked the first time. There aren't any marriage records online for Grant Co, KY in the time period for William A. and Sallie A. Ashcraft's marriage. You should probably write to the Grant Co, KY county clerk to get a copy of their marriage record.
Someone has posted information on Samuel Ashcraft on Rootsweh's World Connect:
There's also a listing for what appears to be your William A. And Sallie A. Ashcraft. However the person who posted it is claiming he's the son of a Robert William Ashcraft. You may want to contact him and compare notes. From the census listings it appears that William A. is the sone of Samuel H. Ashcraft.