Hudson River Trading

HRT looks like a high-frequency firm and then breaks the stereotype: it holds roughly a quarter of its trading capital overnight and averages around five-minute holds, closer to a multi-horizon statistical trader than a millisecond market maker. Founded in 2002 by Harvard and MIT mathematicians and computer scientists recruited away from Silicon Valley, it built its algorithms in-house and treats research and engineering as one team.

From US equities it grew into a principal liquidity provider across global markets, ranking among the top dealers in US Treasuries and running European Systematic Internalisers and a single-dealer platform. Its 2018 acquisition of Sun Trading added connectivity to well over a hundred exchanges. No outside capital, no IPO.