Can't imagine how they transported those huge cables, however long and wide, from Trenton to CA.
The wire rope was shipped on spools and spun into the actual big cables on the bridge. Essentially the Golden Gate was constructed just as the Brooklyn bridge was built half a century earlier.
Cable spinning began in October 1935. To create the cables, Roebling developed a method called parallel wire construction. The innovative technique enabled a cable of any length and thickness to be formed by binding together thin wires. It promised to give engineers the freedom to build a bridge of infinite length.
Loop De Loop
To spin the cables, 80,000 miles of steel wire less than 0.196 inch in diameter were bound in 1,600-pound spools and attached to the bridge's anchorages. A fixture within the anchorages called a strand shoe was used to secure the "dead wire" while a spinning wheel, or sheave, pulled a "live wire" across the bridge. Once it reached the opposite shore of the Gate, the live wire was secured onto the strand shoe, and the wheel returned with another loop of wire to begin the process again.
Largest Cables Ever
Hundreds of wires, each roughly the diameter of a pencil, were bound together into strands. Hydraulic jacks then bundled and compressed 61 strands to make a cable. Each of the two main cables is just over three feet in diameter, 7,659 feet long and contains 27,572 parallel wires. The Golden Gate uses the largest bridge cables ever made -- long enough to encircle the world more than three times at the equator.
http://www.pbs.org/wgbh/amex/goldengate/peopleevents/e_spinning.html
The construction of the Golden Gate was incredibly well documented in film. Here's a vid showing the spinning process.
http://www.videosurf.com/video/wires-on-spinning-wheel-and-people-at-work-in-various-departments-during-the-golden-gate-bridge-construction-in-the-us-1212178122
Check out the related vids for more details.
This still from the vid shows the spools of wire rope:

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