tool-bar-position

tool-bar-position is a variable defined in `tool-bar.el'.
Its value is

top

Documentation:
Specify on which side the tool bar shall be.
Possible values are `top' (tool bar on top), `bottom' (tool bar at bottom),
`left' (tool bar on left) and `right' (tool bar on right).
Customize `tool-bar-mode' if you want to show or hide the tool bar.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.