Gramps 4.0 Wiki Manual - User Directory
The location of your GRAMPS user directory depends on the operating system you are using and how you have set up your computer. In the table below <~username> should be replaced by the name you use to log in to your computer.
On Macs, filenames starting with "." do not show up in Finder. To make access to the Gramps user directory easy, open a terminal window with Finder-Applications-Utilities-Terminal and type there
ln -s .gramps gramps_user_directory
which will allow Finder to show the contents.
The default location for an installation on a Windows system is
C:\Documents and Settings\<~username>\Application Data\gramps