U.S. citizens must apply for residency at the daira (town) Office of Security, which then forwards the application to the wilaya’s (governate) Office of Foreigners. The office for Algiers is:
Bureau des étrangers
20, bd Zighout Youcef
021 73 00 73
Foreign citizens seeking residency must show proof that they have registered their presence in country with their embassy in Algiers. You can show this by bringing the confirmation page from the Smart Traveler Enrollment Program (STEP).