I think these are the Crockards of Comber who lived in Ballygowan and were Presbyterians worshipping at the Ballygowan Presb. Church. There are several places called Ballygowan (MacGavin's settlement)apart from the one in Comber Parish. Map in Ros Davies's web site.
Ballygowan Graveyard. CROCKARD
Erected by Hugh Crockard, San Francisco, Calif., in memory of his mother Martha Crockard who died April 11 1869 aged 66. In Ros Davies there is reference to a Maria Crockard of Comber witness to a marriage in Ballygowan Presb. Church.