Before the late 19th Century beer was brewed with things other than hops. Beer generally needs a bittering agent to offset the sweetness of the malts use in the process, and this is the job that the hops in modern beers perform.
Before the widespread use of hops, ales were flavoured with gruit (somethimes pronounced groot), which uses one or more of a number of herbs including yarrow, mugwort, bog mytrle (aka sweet gale), juniper berries, wild rosemary, sage and others.
I’ve found an excellent resource on brewing gruit ales, along with recipes here.
A Storm Brewing 