The LTD name was first used in 1965, and it was used continually until 1986. It was its own model name starting in 1967. It was always among the more luxurious of the Ford models. From 1975 until 1978, the LTD Landau was a Lincoln-like car still sold as a Ford. Even the headlights were hidden, just like in the Lincoln.
The full-size LTD was produced throughout the late 1970's, but there was also a LTD II sold after 1977. This car was actually a rebodied Ford Torino. By 1983, the car was much smaller than the original, and it was now based on the infamous Fox platform.
Throughout its lifespan, the LTD was used as a police fleet vehicle. The Country Squire Station Wagon was also a popular family option. You might remember a very wacky version of this car as the Family Truckster vehicle in the movie National Lampoon's Family Vacation.
These cars are still readily available on the older used car market. You can find parts for them just about anywhere, but you'll save a lot of money by buying them used or new on eBay.