I guess there are at least two approaches, depending on what you need.
1 - Tile Raster
You could paste a raster tile into the Illustrator file, than drag it into the Swatches palette. Now you can fill any object with this tile.
2 - Vector
Just draw it. You could also do a vector version of the approach above.
To create a 1" square, select the Rectangle tool (M) and click on the artboard. A prompt will open where you can enter the size.
To create a grid out of boxes, make sure Snapping is enabled.
Hold Option(Mac)+Shift and click on one of the points of the box, dragging it to the next position, while utilizing the snapping function.
You now have an operation loaded and you can duplicate by pressing CMD+D, this will repeat the duplicates.
Now you have 1 row (or column). Than do the same with the row to complete the grid.
Another option might be to utilize the Object / Blend function.
Make 2 parallel paths, say 10" apart.
Select both of them and Object / Blend / Make.
Than go into the blend settings and set it to use Specified Steps: 9. This will programmatically generate lines. Might give you some more flexibility.
Just some initial thoughts.
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