I've no idea of the data's provenance, but this table claims aggravated assault rates of 86/100,000 in 1960, 440/100,000 in 1993, and 252/100,000 in 2010 if I've got my math right. Murder rates are 5.08/100,000, 9.51/100,000, and 4.77/100,000 respectively. So the decline in murder since 1993 has outpaced the decline in assault (it also rose less steeply between '60 and '93), and trauma medicine's a plausible cause, but both declines are quite real: I wouldn't say the comparison to the 1960s is valid only because of medical improvements.

In any case, 1960 was more like fifty years ago. The per-100,000 aggravated assault rate in 1980 was just under 300 -- substantially over the 2010 numbers.