The northern boundary of the state with Massachusetts is marked by the Southwick Jog or Granby Notch , an approximately 2.5 mile ( 4.0 km ) square detour into Connecticut .
The northern boundary of the state with Massachusetts is marked by the distinctive Southwick Jog\/Granby Notch , an approximately 2.5 mile ( 4.0 km ) square detour into Connecticut slightly west of the center of the border .