Hollyhocks were introduced to American gardens from the Far East. It has become so common here that most people assume it is a native american plant. The properties of the hollyhock are as a demulcent, emollient and diuretic. The part of the hollyhock that is used is the flower, form which the outer calyx is removed, and flowers then being dried in trays with plenth of air circulation. They turn a dark, purplish black, and may be used medicinally or as a coloring matter.
Hollyhocks seem to have been rather marginal as a medicinal plant and became much more used as an ornamental. I've seen plenty of old outhouses with hollyhocks growing all around them. My outhouse is in too much shade, unfortunately.
Hollyhocks need good drainage and seem to prefer a rich soil. Full sun suits them best. Mine readily self seed and though each plant is somewhat short lived, there are always some that come up every year, though maybe not in the exact place where you have them before. My original plant was a red, but with all of the self-seeding, I now have shades from deep burgundy to pale pink. I haven't had much luck in saving the seed because by the time the seed pods dry, something seems to have bored holes in them and has eaten the seeds. I guess enough of them are missed by whatever eats them to re-seed, but there never seem to be enough to collect.
Seed seems to be readily available, though, from catalogs and in stores, so there's no excuse to miss out on these tall and showy bloom which will continue until frost here.