Apocalypse

[dukealien]

It was routine practice for native Americans to burn the New England forests. The fire cleared the underbrush. English settlers expanding west, in the early days, could ride horses at full gallop through the woods. But the first English to travel west from the colonies weren't men. They were disease. Smallpox annihilated many tribes, leaving desolated, pristine acres behind.  

A young family traveling out into the wilderness, therefore, would have been greeted with open fields, populated by troves of animals, their numbers unchecked by hunters who now, in strange poses, had wasted into skeletons, which could be found grouped in lifeless encampments, prone in empty fields, contorted and hunched alone against a tall tree in a New England cathedral forest, where a child might accidentally find them, and perhaps leave breathless and horrified, holding strange jewelry, or a knife, or a bone, wondering how to keep it secret, or what sin they may have done in the eyes of their violent, reckless Christ.

In basic critique, and taking this as a prose poem, I'd say it reads like a somewhat novelized history text by a competent or better-than-competent author.  That's good:  it gets its point across and contains striking images.

Some of the images could perhaps be improved:  for example, by making the point that they could ride at a gallop through the burnt-out woods among healthy trees, only the tangling creepers and underbrush having been consumed (as in any natural forest fire).  Another point might be that the native Americans did not have this purpose in mind since they had no horses until the Europeans brought them.

There are a few cliches, which are hard to avoid in expository writing:  "greeted by," for example.  Number (singular/plural) does not match in the short sentence, "They were disease."  Strictly speaking, both should be plural (to agree with the previous sentence), i.e. "They were diseases."

Your second paragraph is one sentence which could easily be converted into blank verse by line breaks, thus:

A young family traveling out into the wilderness, therefore,
would have been greeted with open fields, populated
by troves of animals, their numbers unchecked
by hunters who now, in strange poses, had wasted
into skeletons, which could be found grouped
in lifeless encampments,
prone in empty fields,
contorted and hunched alone against a tall tree
in a New England cathedral
forest, where a child might accidentally find them,
and perhaps leave breathless and horrified, holding
strange jewelry, or a knife, or a bone,
wondering how to keep it secret,
or what sin they may have done
in the eyes of their violent, reckless Christ.

(Example only.)  The final thought, "what sin they may have done in the eyes of their violent, reckless Christ," is unclear in its use of "they" and "their" - can be confusing, particularly on first reading.  It might be worth specifying that the imputed sins were by the native Americans and the Christ of "their" was of the Europeans - who felt, catholically, that sins were so punished even when committed by "heathens" whom the Europeans' gospel had not reached in time.  The final adjective ("reckless") seems to need more support if the prose-poem is meant to be expository, but in an art-poem serves as a late turn from description to author's judgement.  As such, it is effective.