The latest release of the original X11 distribution can
be obtained from ftp.x.org, or see
http://www.x.org/download.htm
for a list of ftp mirror sites.

Most free systems now use the XFree86 distribution.
XFree86 is available from ftp.xfree86.org/pub/XFree86,
or see the www.xfree86.org web site for information
on mirror ftp sites.