|New York City, 1872|
Using city directories and phone books, you can follow a family year by year and find clues about children, marriages, deaths, and relocations. Many city directories have been scanned and are available free at the Internet Archive. Footnote.com and Ancestry.com also have significant collections of directories.
Voter registrations are another good way to track a person through time. Registrations used to be done every two years. The registration commonly included name, age, address, occupation, and party affiliation. Some include birthplace and naturalization information. The Family History Library has filmed some voter registrations, and Ancestry.com has a small collection, including California voter registrations ranging from 1900-1968.
After you have addresses for where your relatives lived, you can locate them on maps. Current and historical maps may also show nearby churches, schools, and cemeteries, which could be sources of more information. Fire insurance maps, such as the Sanborn series, can tell you building dimensions, composition, number of stories, and more. Many of the Sanborn maps are now digitized and available online, such as the collection available through the San Francisco Public Library (viewable at home with an SFPL card).
Even though your relatives may not have owned real estate, you might find them on tax lists for personal property, poll/head/voting, income, and occupation. Taxes could be collected at the local, state, and national levels. Tax records can provide direct evidence of occupation and property ownership, and indirect evidence of age, marriage, death, relationships, and moves. Most tax records are not available online, though some may be found on Ancestry.com and FamilySearch.org. The Family History Library has filmed many county tax records, however, which can be ordered and viewed at a local Family History Center. Tax records may also be found at state archives, state and county libraries, and county courthouses.
You may also find your relatives on membership lists -- fraternal organizations (Masons, Knights of Columbus), veterans groups (Grand Army of the Republic), lineage societies (DAR, UDC), alumni directories, ethnic societies. Society records may include applications, biographies, photographs, memoirs, and activity reports. Many groups now have Web sites; some have instructions online for how to order copies of their information.
Petitions are lists of signatures from people who wanted to change something. The lists can document residence, military service, and land ownership. They can indirectly show age and family relationships. The National Archives has thousands of original petitions. State archives can hold local petitions.
Your relatives should show up in at least one of these resources, if not more. And with each additional piece of information you find, you build a better picture of your family in the context of their time.