Drawings by Isambard Kingdom Brunel, blueprints by Robert Stephenson and designs by Joseph Locke, William Henry Barlow and other engineering giants of the 19th-century railway boom will go on permanent display for the first time in a new online archive.

Giant projects covered in the archive include the Forth and Tay bridges, Brunel's Box Tunnel, and major stations including Paddington with its beautiful swirling iron and glass end screen.

Network Rail inherited a giant archive of more than 5m records dating back more than three centuries – the oldest predate the railways, and go back to a document from 1680 signed by Sir Christopher Wren dealing with a plot of land which would later become Charing Cross station – from its predecessors.

The archivist, Vicky Stretch, said: "The drawings and documents are a window to understanding the incredibly detailed and beautiful; are an absorbing window to understanding the incredibly detailed and beautiful architectural work carried out by some of the world's greatest engineers; and are still important for engineers working today."

Some of the records are still in operational use, such as Brunel's Box Tunnel drawings, as they show details crucial for maintenance such as foundations and construction details.

Only a fraction of the archive is going online in the first phase, but more images and documents will be added – and questions can be sent to the archivist through the site.