Quoting by permission from the United Empire Loyalists' Association of Canada website:
"The Mission and Objectives of the UELAC direct that we work to preserve and promote Canadian history, with a particular focus on the Loyalist timefame of the late eighteenth and early nineteenth centuries. Loyalist heritage takes many forms from actual buildings of the time to family histories, genealogies, stories, military records, monuments, artifacts, correspondence and so much more.
Very simply, the general guidelines are as follows:
Either male or female, as of 19 April 1775, a resident of the American colonies, and joined the Royal Standard prior to the Treaty of Separation of 1783, or otherwise demonstrated loyalty to the Crown, and settled in territory remaining under the rule of the Crown; or a soldier who served in an American Loyalist Regiment and was disbanded in Canada; or a member of the Six Nations of either the Grand River or the Bay of Quinte Reserve who is descended from one whose migration was similar to that of other Loyalists. As noted these are general guidelines. If you think you may have Loyalist ancestry, why not join and undertake the journey – at a minimum you will learn more about your family."
US researchers with ancestors who were Loyalists are welcome to join this organization. An excellent publication 'The Loyalist Gazette' is published twice a year.
Follow this Contact link for more information or to join the organization.