The benefits of using superconducting radio-frequency (SCRF) acceleration for an
electron-positron linear collider have been well documented over the years. The ultra-low cavity wall losses allow the use of long RF pulses, greatly simplifying the RF source, while facilitating high-efficiency acceleration of high-current beams. In addition the low RF frequency (1.3 GHz) significantly reduces the impedance of the cavities, leading to reduced beam dynamics effects and relatively relaxed alignment tolerances. Over two decades of R&D has lead to an increase in the deployed available gradient of over a factor of six, which, together with a high level of cavity integration into single cryostat
(cryomodule) has resulted in an affordable and mature accelerator technology. Following a unique decision in 2004 by the world high energy physics community to develop the International Linear Collider (ILC) based on the established SCRF technology as a truly global project, the Global Design Effort (GDE) has successfully coordinated a worldwide R&D programme which will culminate in the ILC Technical Design Report in 2013. This presentation will chart the history of the SCRF linear collider, with a focus on the quest for higher gradients (35 MV/m and beyond), the ‘globalisation’ of the technology, and the preparation for a worldwide industrial base for the construction of the ILC.