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.
The default location for an installation of GRAMPS in a POSIX-style environment is /home/<~username>/.gramps. This is true for BSD, Linux, Solaris, Unix and OS-X.
The default location for an installation on a Windows system is C:/Documents and Settings/<~username>/.gramps