Usenet as of April 15, 1981:

                                  pdp
                                   |
           decvax sii  reed  phs--unc--grumpy  duke34
              | |  |    |     |    |             |
              | +--+----+-----+-+--+-------------+
              |                 |
              |               duke
              |                 |
              |          +------+---+----------------+------+-------+
              |          |          |                |      |       |
     ucbopt   |         mhtsa    research   mh135a hocsr  chico---harpo
        |     |          |  |                  |
     ucbcory  |          | eagle    ihnss   vax135  (Bell Labs Sites)
        |     |          |  |        |         |
     ucbvax---+----------+--+--+-----+--+------+--------+
        |                      |        |               |
     ucbarpa               sdcsvax      |             menlo70--hao
        |          sdcattb-----+        |               |
     ucbonyx                   +-----ucsfcgl          sytek
                   phonlab-----+
                            sdcarl