Final answer:
The dependent clause in the sentence is 'until local citizens demanded changes to the law'.
Step-by-step explanation:
The dependent clause in the given sentence is "until local citizens demanded changes to the law". A dependent clause cannot stand alone as a complete sentence because it does not express a complete thought. It relies on an independent clause to complete its meaning. In this case, the dependent clause provides the reason or condition for the council members amending the city ordinance against picnicking in the park.
Learn more about Identifying dependent and independent clauses