The United States Citizenship and Immigration Services (USCIS) posts historic processing times (i.e. wait times) online all the way back to 2017 here. This link allows an immigrant to track the processing times for almost all immigration petitions. It is also possible to check processing times based on the specific USCIS field offices or processing centers at Processing Times. Even more specific information is available to people with pending requests if they go online and enter their receipt number at USCIS Case Status.