Are you a beginner research who wants to take the 'next-step' in researching your family after discovering them in census records? City Directories are your next stop on the genealogical research journey to fill in the gaps between the census records or to extend a person's life after a record trail ends.
Ancestry.com is my go-to resource for City Directories online. I have accessed city directories in state repositories, which is great. However, there's no reason to make an in person visit to a library to access a bound book if a digitized version of that same book is available online.
Do you have a relative who disappears from census records 10 years after your last record of them? Follow them through city directories and you might discover within 1-2 years when they left that location. You won't know where they went, but at least you know when.
Do you know when a particular ancestor changed residences? Following an ancestor through city directories can help you determine which year your family may have purchased a property. That knowledge helps narrow your land records search for deeds of sale or purchase.
Do you know when your relatives changed occupations? By following an ancestor through city directories, you might discover they weren't always the milkman. Perhaps they did a stint as a bar tender or an ice delivery truck driver.
In the post Sherman Brown and the City Directories, I detail exactly how much information I gleaned from the records and how amazing the discoveries are. Read that post (here) and then go find your ancestors in the directories!