Strong room temperature visible (red-orange) photoluminescence (PL) has been observed in silicon nanowires (SiNWs) that were realized by wet chemical etching of heavily (arsenic, As: 1020$\hskip0.3em${}cm$-${}3) and lowly doped (boron, B: 1015$\hskip0.3em${}cm$-${}3) single crystalline silicon (Si) wafers. Optical characterization of these SiNWs by PL combined with structural characterization by transmission and scanning electron microscopy strongly suggest that the visible PL at room temperature results from the rough SiNW sidewall structure that is composed of nanoscale features in which quantum confinement effects may occur.