His family must've come here in the latter half of the 1800s,
In 1880, a less common occupation for the Gump family was Keeping House. The most common Gump occupation in the USA was Farmer. 42% of Gump's were Farmers. Farmer, Farming and Farm Laborer were the top 3 reported jobs worked by Gump.
Ironically, rhymes with a name most familiar to readers here, origins of middle English.
In 1880, a less common occupation for the Trump family was Carpenter. Farmer, Laborer and Keeping House were the top 3 reported jobs worked by Trump. The most common Trump occupation in the USA was Farmer. 38% of Trump's were Farmers.
Which gang did they join upon arrival to Five Points? Trump would've most likely been in the Bowery Boys with Bill the Butcher. Gump probably would've been in the Plug Uglies.