首先,英語中有一個規(guī)定就是一般不會在句尾放介詞（介詞后面一定有名詞）.所以在碰到從句的時候,特別是which或者that所指代的詞在從句中視作為介詞后面的名詞出現(xiàn)的時候,就必須用which,并將介詞前置.
which在這里是指代那個the city of Washington的,后面的從句的應(yīng)該寫成the village of Georgetwon was the market center for the city of Washington.
明白了嗎?給你舉個例子
His first job is in a big bank,from which he learnt a lot of information about financial management.
which是指代bank的,后面的從句是說he learnt a lot of information about financial management FROM the BANK.
所以不存在for which的用法,只是介詞加which的用法.