Eagle cad, choosing mm as default
EAGLE stores the grid setting within each board file, so when you open any board, you get the grid settings used last time you saved this board.

However, it is possible to configure EAGLE with custom values, which are used whenever you create a new board.
Within the EAGLE installation directory, there is the file scr/eagle.scr, which looks like this:


BRD:
MENU '[designlink22.png] Search and order : Run designlink-order.ulp -general;'\
     '[pcb-service.png] PCB Service : Run pcb-service.ulp;'\
     '[idf-3d.png] Export to IDF 3D format: Run eagleidfexporter.ulp;'\
GRID INCH
GRID 1
;




SCH:
Grid Default;
Change Width 0.006in;
MENU '[designlink22.png] Search and order {\
                                          General : Run designlink-order.ulp -general; |\
                                          Schematic : Run designlink-order.ulp; \
                                          }'\
;


It contains several sections for several windows (my snippet shows only BRD and SCH for board an schematic).
I've added two lines to the BRD section to set the grid unit to inch and step width to 1 and proved that I indeed get a 1" grid for new boards. (EAGLE 7.4.0)
Possible units are:

GRID MM (Millimeter)
GRID MIC (Micrometer)
GRID MM
GRID MIL