Here is an interesting quote from Yahoo answers that I discovered.

"It is probably not of much help, but in the 19th century the was quite a rivalry - particularly between the UK and USA - to build railway locomotives (at that time steam locomotives of course) in the shortest time. By 1890 the record stood at 25 hours 30 minutes. However, in all cases, the clock had not been started until many of the major components were already assembled - frames, boilers etc. In December 1891 the Great Eastern Railway on the UK decided to make an attempt at their workshops at Stratford in east London. It was decided to start from scratch, and a total of 16,9452 individual parts were assembled, the locomotive painted in undercoat and steam raised in the total time of 9 hours 47 minutes, a total of 142 men and boys being involved. This World record has never been beaten. Interestingly, the railway complex at Stratford is now part of the Olympic Park in London - very few of the visitors in 2012 would have been aware that an un-beaten World Record had been set on the site over 120 years beforehand! "