The Arpanet has 15 Nodes (1971)

In 1971 the ARPANET had 15 nodes (23 hosts).  They were: 

UCLA

Stanford Research Institute

University of California, Santa Barbara

University of Utah

Bolt, Beranek and Newman (Cambridge, Mass)

MIT

The Rand Corporation (Santa Monica)

Software Development Corporation (Santa Monica)

Harvard

Lincoln Laboratory (Lexington, MA)

Stanford

University of Illinois at Urbana-Champaign

Case Western Reserve University

Carnegie Mellon University

NASA/Ames Research Laboratory.