The boundary lines of Local Union No. 1 consist of the following which have been mutually agreed to by the local unions surrounding same.
- On the North, the Wisconsin State Line.
- On the Northwest, from County Line on Route 53, follow Cook County Line to McHenry County, West on Kane County Line to Route 31, North on Route 31 to Route 14, Northwest on Route 14 to Route 47, Route 47 to the Wisconsin Line. Territories East of the Routes belong to Local Union No. 1.
- One the West, Illinois Route 53 from Cook County Line along the Eastern City llimits of Glen Ellyn; South to 31st Street, then east on 31st Street to the Eastern City limits of Downers Grove; South on Fairview Avenue onto Route 66, then East on 91st Street to Clarendon Hills Road; South on line with Clarendon Road to Cook County Line.
- On the South and Southwest, Will County Line.
- On the Southeast, Indiana State Line