...the creation of FORTRAN? Looking at the entry for 1956, the site lists MIT creating the TX-0, the "first general-purpose programmable computer built with transistors", and IBM's shipment of "RAMAC", the first computer based on "The new technology of the hard disk drive".
In the mid 50s silicon transistors started to replace vacuum tubes. I assume tubes were at their cheapest in the late 50s. I'm not sure why the article uses '57 in particular though.