Finding maps for land research

Use maps maps and more maps

Use the Atlas of Historical County Boundaries to see if the county was the same when he would have gotten his patent because it visually shows you what the state looked like at a given time.

Use the Libre Map Project to zero in on Township & Range or specific areas (slow to load but worth it)

PLAT MAPS

start with Google

"Yuma County" Colorado ~plat map

historic ~atlas "Bucks County" Pennsylvania

look at both the web results AND the image results view

large collections that have many plat maps:

If you have Ancestry they have a very large collection of plat maps here is the link

Historic Map Works Collection - they sell these maps but you can look at them without buying

Internet Archive

Library of Congress Map Collection

examples of some collections and guides for specific states

If they lived in a town don't forget to search for a city directory.