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Is the following sentence written correctly?

If you were not from the small town of Sandtown, located in Delaware, most likely, you wouldn’t have known it existed, as the large trees and heavy brush had overrun it long ago.
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I'm sure people will disagree on this.
I suppose it's correct, but It would be a lot more comfortable if the "knowing" and the "being" were in the same tenses.

Then, we have to wonder if "were" is present subjunctive or simple past: "If it were a bear it would bite you." "If it were a bear, it would have bitten you." (both correct)

To be something and to know something are sort of continuous conditions. If I'm from Sandtown, I'm always from Sandtown, and if I know about Sandtown, I'll probably always know about Sandtown.

The speaker is obviously speaking about a past situation (had overrun it long ago), so I'd think the past perfect would be in order:
If you had not been from Sandtown, you wouldn't have known it existed.
Under different circumstances, you could use the present:
You're from Sandtown. But if you were not, you wouldn't know it exists/existed [to see it now].

Another unknown is whether or not the speaker considers that at some point Sandtown ceased to exist. When the unspecified "past event" occurred, did the overgrown town still exist as a legal entity? Did it exist as a ghost town?

I suppose we have to give the speaker some latitude, because we don't know what's in his mind.
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It seems to me that "it existed" should be "it had existed".

I'm also not keen on the ambiguously placed and awkwardly punctuated "most likely". I think I'd write "... you most likely wouldn’t ...".
I'm still struggling with the tense problem, If you were X, you wouldn't have Y. The more I read it the more I'm inclined to say that with proper context it would be perfectly natural.
If context establishes both the present tense and the missing past event, It should fly.
"If you were white, you wouldn't have been afraid."
i think mixed conditional is possible here
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