[文法] being開頭的句子

[petroleum1 (viceroy)]

By 1910 most Americans lived in towns and cities,
being the frontier had mostly disappeared.

想問為何第二句前面要有being ?

用意是?

有人說是同位語，那照理說可以用which或that取代，但也不是

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→ kaifrankwind: http://www.thefreedictionary.com/being see conj.
推 ms43: Being 這半句 肯定是寫錯的
→ wohtp: 這是完整的句子嗎？
推 priv: 如果寫 being that 就比較沒爭議，MW 上寫 conjunction 用法
→ priv: 是 chiefly dialect
推 GGininler: being (that)~that應該是被省略無誤