### Clue: Recollected Nixon's ad associated with oil men – it divided America (5-5,4)
### Answer: MASON-DIXON LINE 
 ### Explanation: Definition: it divided America
 **Anagram of**(Recollected) [NIXON'S AD **plus**(with) OIL MEN].
Answer: Named after 2 Britons, astronomer Charles Mason and surveyor Jeremiah Dixon, who marked it following resolution of a border dispute between then British colonies in America.