Tell your wife to head for the kitchen sink: You win.
The $6 million 266-room Hacienda Hotel and Casino opened at the far south end of the Strip, across from McCarran Airport, in June 1956. It was one of a chain of California low-rise motor inns, just far enough off the beaten track to pursue its own course along the rocky road of hotel competition in the mid-1950s in Las Vegas.
It catered to low rollers and families, mostly from southern California. Its "Hacienda Holiday" billboards were prominently placed along West Coast highways. Privately owned and operated DC-4 airplanes shuttled in customers in high style, taking advantage of the Hacienda's location; the Hacienda also chartered fleet of tour buses. It also boasted the Strip’s first heliport. A rebate of $10 in play money greeted arrivals. The adult entertainment budget was minuscule, spent on a go-kart track instead, while the pool area was large and luxuriously landscaped. The Charcoal Room was one of the best old-school bargain-gourmet rooms in town.
I's unclear exactly when, but the Hacienda also opened its Camperland RV Park and Campground. If you were driving in from southern California, it was the first you came to when approaching the Strip.
The Hacienda was sold to what at the time was Circus Circus Enterprises, which razed the whole property to make room for Mandalay Bay.
Meanwhile, as far as we know, the El Rancho never had an RV park. However, right across the street, Circus Circus had and still has one of the largest RV parks in Las Vegas, with nearly 500 spaces. So perhaps your wife's recollection has something to do with the RV park on the north end of the Strip, rather than the south.