I started on CAD - Computer Aided Drawing, back in mid 1984, using an Australian written piece of software written by engineers and draughtsmen in Queensland, called "Palette". Ran on a macro/mini computer which was similar to bj describes, around the size of two microwaves, back to back, tape backup etc. We ran 4 terminals off ours and our project ran 12 terminals. Had 15 layers which could be worked on by different stations simultaniously. Cost per computer and 4 terminals in 1984, not adjusted figure, $100,000aud, adjust that to todays numbers will give some idea how expensive they where.
You selected the sheet size you wanted, pen thickness, and away you went drawing.
No PC's then to run on. I had a Tandy, colour computer then. My current hand calculator is more powerful than them.
Mid 1985, I started using Autocad v 2.8, real stupid piece of software written by American programmers, who had not a lot of knowledge of draughting. Paperspace/model space didnt arrive until very early 1990, if memory serves with I think v10. sorta useful from then onwards.
I worked at a ship-builders in South Australia, 1987, when they purchased an "Intergraph" 3D CAD package from someone in Victoria, came in 2 containers, one for the computer itself, the other containing the 4 dual screen workstations. Was considered "old" then, but they used it for a quite a number of years to design and build ships. Would have used it for the submarine project but they missed the selection. All they built was the ship lift and buildings for the Sub-Corp.
So, yes, CAD does go back a ways, but its only comparatively recently that affordable 3D packages have been available for the average draughtsman at home. Prior to that, companies had to have huge budgets for big jobs to justify them.
Just as an aside, I started working in 1967, at the NZ Ministry of Works, that same year they installed a computer for engineering design, no drawing. Cost $1,000,000nzd, in 1967 dollars, and took up the whole basement of a new 14 story building. Tape input, and wardobe size cabinets with the tape reel window. All in airconditioned rooms. You punched your cards, checked them, took them down, next day you went down to collect the tractor feed continuous printout, with a trolley. To big to carry, man this forests took a hammering back then.