GMAT-Prep RC: Final solution at one place:

Maps made by non-Native Americans to depict Native American land tenure, resources, and population distributions appeared almost as early as Europeans' first encounters with Native Americans and took many forms: missionaries' field sketches, explorers' drawings, and surveyors' maps, as well as maps rendered in connection with treaties involving land transfers. Most existing maps of Native American lands are reconstructions that are based largely on archaeology, oral reports, and evidence gathered from observers' accounts in letters, diaries, and official reports; accordingly, the accuracy of these maps is especially dependent on the mapmakers' own interpretive abilities.

Many existing maps also reflect the 150-year role of the Bureau of Indian Affairs (BIA) in administering tribal lands. Though these maps incorporate some information gleaned directly from Native Americans, rarely has Native American cartography contributed to this official record, which has been compiled, surveyed, and authenticated by non-Native Americans. Thus our current cartographic record relating to Native American tribes and their migrations and cultural features, as well as territoriality and contemporary trust lands, reflects the origins of the data, the mixed purposes for which the maps have been prepared, and changes both in United States government policy and in non-Native Americans' attitudes toward an understanding of Native Americans.

The passage suggests which of the following about most existing maps of Native American lands?
(A) They do not record the migrations of Native American tribes.
(B) They have been preserved primarily because of their connection with treaties involving land transfers.
(C) They tend to reflect archaeological evidence that has become outdated.
(D) They tend to be less accurate when they are based on oral reports than when they are based on written documents.
(E) They are not based primarily on the mapmakers' firsthand observations of Native American lands.

Key Takeaways from the passage...

1. The author is primarily talking about the Non-Native American maps that depict Native American lands
2. S/he mentions the origins of the information used to make the maps
3. S/he mentions that the map creators used interpretive abilities rather than firsthand information to create the maps

Refer to the quoted text below:

"accordingly, the accuracy of these maps is especially dependent on the mapmakers' own interpretive abilities."

This clearly suggests that the maps creators did not have firsthand information on native american lands. Hence option (E) is the right option.