Fun Question: Need assistance setting up a WAN between two warehouses

You have been been given the task of creating a WAN link between your LAN and a new building located 2 miles down the road. The existing LAN has 5 departments (Wholesale, Corporate, Warehouse, IT/ Creative, and Retail) with 20 users in each which 3 of the departments will be moving into the new building. Please walk me through step by step of the system you would implement to not only connect the other building via T1 connection but to create a more agile work enviroment for all the users the previous admin has a one subnet setup for all users. Be creative and try not to look at the responses for hints.