The two largest legacy agencies that came over to Customs and Border Protection were: Immigration and Naturalization Services and Animal and Plant Health Inspection Service U.S. Customs and the Border Patrol Department of Treasury and Department of Justice Border Patrol and U.S Marshals

1<br />The question is asking about the two largest legacy agencies that were integrated into the U.S. Customs and Border Protection (CBP). The CBP is a part of the Department of Homeland Security, which was created in response to the September 11, 2001 terrorist attacks.<br />## Step 2<br />The two largest legacy agencies that were integrated into the CBP were the Immigration and Naturalization Services (INS) and the Animal and Plant Health Inspection Service (APHIS). The INS was responsible for processing immigrants and refugees, while the APHIS was responsible for protecting the United States' agriculture and natural resources.<br />## Step 3<br />The other options provided, such as U.S. Customs and the Border Patrol, Department of Treasury and Department of Justice, and Border Patrol and U.S Marshals, are not the correct answer because they were not the two largest legacy agencies that were integrated into the CBP.