Click on USCIS website link below, then choose appropriate Service Center at bottom of the USCIS web page: Latest processing times at USCIS Service Centers
 
At which USCIS Service Center is my petition filed?
Some applications/petitions are filed according to the state of employment or residence, others are filed based on the type of filing. Your filing receipt number will indicate which Service Center receipted your application/petition: WAC stands for Western Adjudication Center (California Service Center), EAC for Eastern Adjudication Center (Vermont Service Center), LIN for Lincoln (Nebraska Service Center), TSC for Texas Service Center, and NBC for National Benefits Center (Missouri Service Center).

If your application/petition was filed according to the state of employment or residence, you can look up your Service Center using the USCIS Service Center Locator (click on the state where your employment is located, and the “Service Center” column will show the USCIS Service Center where your petition was most likely filed). Note that there are some applications that must be filed with a specific Service Center regardless of where an applicant or petitioner lives; also note that applications/petitions may be transferred among the various Service Centers depending on backlog workload.