The bottom-up spatial organization of potential nanoelectronic components is a key intermediate step in the development of molecular electronics. We describe robust three-space-spanning DNA motifs that are used to organize nanoparticles in two dimensions. One strand of the motif ends in a gold nanoparticle; only one DNA strand is attached to the particle. By using two of the directions of the motif to produce a two-dimensional crystalline array, one direction is free to bind gold nanoparticles. Identical motifs, tailed in different sticky ends, enable the two-dimensional periodic ordering of 5 and 10 nm diameter gold nanoparticles.