Those interested can consult a list of doctoral dissertations in progress
in the USA at the website of the American Historical Association and a list
of dissertations and theses, in progress and completed, in the UK at the
website of the Institute of Historical Research.  Both lists have the
limitation of being confined to history department research and exclude
those in other relevant disciplines such as American studies, literature,
and religion.  I don't know whether there are similar Internet lists for
other countries such as Canada and Australia.  It is hard to locate
American master's theses while they are in progress.  The most complete
listing of completed work is WorldCat, a web-based library list.  Often
titles reach WorldCat belatedly when dissertations and theses are cataloged.