We present results from a multi-year monitoring campaign of the broad-line radio galaxy 3C 120 , using the Rossi X-ray Timing Explorer ( RXTE ) for nearly five years of observations . Additionally , we present coincident optical monitoring using data from several ground-based observatories . Both the X-ray and optical emission are highly variable and appear to be strongly correlated , with the X-ray emission leading the optical by 28 days . The X-ray power density spectrum is best fit by a broken power law , with a low-frequency slope of -1.2 , breaking to a high-frequency slope of -2.1 , and a break frequency of \log \nu _ { b } = -5.75 Hz , or 6.5 days . This value agrees well with the value expected based on 3C 120 ’ s mass and accretion rate . We find no evidence for a second break in the power spectrum . Combined with a moderately soft X-ray spectrum ( \Gamma = 1.8 ) and a moderately high accretion rate ( \dot { m } / \dot { m } _ { Edd } \sim 0.3 ) , this indicates that 3C 120 fits in well with the high/soft variability state found in most other AGNs . Previous studies have shown that the spectrum has a strong Fe K \alpha line , which may be relativistically broadened . The presence of this line , combined with a power spectrum similar to that seen in Seyfert galaxies , suggests that the majority of the X-ray emission in this object arises in or near the disk , and not in the jet .