DataGrid View Checkbox question

Hello,
I am trying to populate a checkbox column in a datagridview control when my form loads.
I am using the following code snippet
 foreach (DataGridViewRow row in gvLocation.Rows)
        {
            row.Cells[0].Value = true;
         }

I have also tried
for (int i = 0; i < gvLocation.RowCount; i++)
    {
        gvLocation.Rows[i].Cells[0].Value = true;
    }
I can see the value of the cell to be true in the watch window but I am not able to see the checkbox
as checked in the grid, Can anyone let me know what I am missing.
 
Chase