Combining biomolecular function with integrated circuit technology could usher in a new era of biologically enabled electronics. A key challenge has been coupling different molecular functions to specific chip locations for communication with the circuit. We used spatially confined electric fields to assemble different populations of DNA-coated nanowires to desired positions with an accuracy that enabled postassembly fabrication of contacts to each individual nanowire, with high yield and without loss of DNA function. This combination of off-chip synthesis and biofunctionalization with high-density, heterogeneous assembly and integration at the individual nanowire level points to new ways of incorporating biological functionality with silicon electronics.