In a tree I am working on - the living narrative tells me some ancestors came on "the gravy boats" from the USA in the early 20th century ................ what were these boats, did they even exist, and are the incoming passenger lists available?
For "gravy boats" I would suggest you read "gravy train" which is used for the situation where someone does very little work to achieve a sizeable income. Whether the economy in the early 20th century was better over here than in the USA I'm unsure about, but I suspect that this is simply a descriptive situation where the grass may have been greener economically on this side of the Atlantic at that time.