The serious study of Atlantis - Atlantology as it is called by some - is said to have started with the book Atlantis: the Antediluvian World by Ignatius Donnelly published in 1882. Donnelly does indeed deserve much credit for his seminal book which did elicit much interest. Probably his book still has much value today.
Interestingly, though, there has been a Theosophical hand behind the dissemination of the Atlantis story and that is traced here.
Atlantis was first brought to the attention of the West by Plato. Blavatsky says Plato was an initiate and obtained his information on Atlantis as part of his initiation. She says his attribution of his information to his grandfather, Solon, was to disguise the source of his information.
Plato described Atlantis in two of his dialogues, the Timaeus and Critias, placing it "west of the straits which you call the pillars of Hercules", i.e. in the Atlantic Ocean. Thomas Taylor, who was responsible for bringing these two dialogues into what he called a "modern" tongue, was himself very appreciative of the mystical and occult side of Plato's writings. Blavatsky said that Jowett knew more Greek but Thomas Taylor knew more Plato. Finally in 1793 Thomas Taylor brought the substance of these dialogues into English. Taylor writes in his introduction:
It is a singular circumstance, that though there is not, perhaps, any thing among the writings of the ancients which has more generally attracted the attention of the learned in every age than the Atlantic history of Plato, yet no more than one single passage of about twenty or thirty lines has, prior to my translation of the Timaeus, appeared in any modern language. (Thomas Taylor, Introduction to Critias, published along with Timaeus and other dialogues in 1793. The Critias was not translated by Taylor until 1804.)
In 1882 Ignatius Donnelly published his seminal book Atlantis. In an appreciative foreword to a 1949 edition of that book, H. S. Bellamy says:
The discussion of Plato's myth in antiquity and in the Middle Ages was purely literary or philosophical and hence did not result in the advancement of Atlantis theories. ... Benjamin Jowett [The "standard" translator of Plato's works], could say with apparently every justification that Atlantis was probably never more than "an island in the clouds which might be seen anywhere by the eye of faith." ... It was only in the early eighteen-eighties, more than twenty-two centuries after Plato told his great wonder-tale, that Atlantology can be said to have started. Donnelly's tremendous book made further fantastic speculation impossible, and set the compass for real and serious research. (Ignatius Donnelly, Atlantis The Antediluvian World p xiii 1949, a preliminary statement by H. S. Bellamy )
However, Bellamy overlooked the hand of Theosophy in the late 19th century. Blavatsky mentioned Atlantis numerous times in Isis Unveiled, written in 1877. There she gave out hints, and details of Atlantis and commented favorably on its existence. (See Isis Unveiled i413, i529, i545, i557-8, and i590-5.) IUi557 says,
The perfect identity of the rites, ceremonies, traditions, and even the names of the deities, among the Mexicans and ancient Babylonians and Egyptians, are a sufficient proof of South America being peopled by a colony which mysteriously found its way across the Atlantic. When? at what period? History is silent on that point; but those who consider that there is no tradition, sanctified by ages, without a certain sediment of truth at the bottom of it, believe in the Atlantis-legend. ... There are, scattered throughout the world, a handful of thoughtful and solitary students, who pass their lives in obscurity, ... These men believe the story of the Atlantis to be no fable, but maintain that at different epochs of the past huge islands, and even continents, existed where now there is but a wild waste of waters.
Did Donnelly read her book and then embark on a gathering of the facts for his own book which was published five years later? Is there a reason why his book came out then - when the issue had previously lapsed for twenty-two centuries? Blavatsky's writings were achieving considerable notice and anyone interested in Atlantis would likely have encountered her work. Interestingly, Isis Unveiled on i591 quotes page 179 of Baldwin's "Prehistoric Nations" on the origin of the name Atlantis. Baldwin traces the name not to the Greek Atlas, but to the Central American word atl, meaning water and war. Blavatsky is there bringing forward further interesting evidence to link the old and new world, and to suggest the reality of Atlantis. Five years later Donnelly agrees and references the exact same quote from Baldwin in his chapter "Corroborating Circumstances". Six years after Donnelly's book, Blavatsky published the SD, praising Donnelly's book and directing still more attention to it.
Would it not be fair to say that while Donnelly wrote the seminal book on the specific subject of Atlantis, Blavatsky, with all the world-wide attention she received, should be the one to receive the true credit for initially igniting the present-day interest in the subject?