John Burke (12 Nov 1786 – 27 Mar 1848), an Irish genealogist, and his son Sir (John) Bernard Burke (5 Jan 1814 – 12 Dec 1892), a British genealogist, jointly and severally established the genealogical publishing tradition which flourishes to this day. The scope and detail of their coverage of what might be termed the upper and middle sections of society in the British Isles was simply staggering.
For present purposes, it is their series of publications on the landed gentry of these islands which are particular relevant. The first such title referred to commoners rather than landed gentry, though the title page took care to emphasise that commoners were not "common people" but rather patricians who didn't happen to have heritable titles – in the same way that Parliament was divided between the House of Commons and the House of Lords. Such was the restricted suffrage of those days that the landed gentry provided both the electorate and the elected to the House of Commons.
It is said that the landed gentry are in terminal decline, but as long as there is land there will be people who own it, whether or not they are "old money" or "new money". And indeed, it's probably the phrase itself which is obsolescing.
A more important distinction is the scope of coverage – initially these publications covered both Great Britain (England, Wales and Scotland) and Ireland. But at the end of the 19th century (1899 in fact), for whatever reason, Great Britain and Ireland started to be covered separately.