- The tradition is that three Lansdale brothers immigrated from England to Prince George's and Lower Montgomery Counties; this seems to have happened around 1700, give or take a decade (probably give). According to Henry Hutton's notes, two were apparently named William and Thomas. If these names are correct, I don't know whether John was the third, or (his son) Isaac—I’d assume the latter, since he was born in England and died in Maryland. Hutton also goes on to say that William was "the father of Dr. Philip Lansdale and Mrs. Ed. B. Duval"—he's referring to William Moylan Lansdale (I4036) here.
According to Effie G. Bowie, "Isaac Lansdale I, born in Leicestershire, England, about 1686; settled at Queen Anne, Prince George's Co., MD where he owned a plantation, "Rich Thicket"; merchant; imported goods from Philip South of London; Warden of Queen Ann parish; vestryman; d. before August, 1733, in which year Thomas Lancaster, his wife's brother, administered his estate. He marryed Margaret, daughter of Richard Lancaster, merchant of London and Prince George's County."
According to Barnes, he "arrived in Maryland by 1719" and was "in PG Co. by 3 March 1725 when he was listed as a creditor of Susannah Mitchell. He d. by 10 July 1734 when Thomas Lancaster was mentioned as his admin." [2, 3, 4]