...and after a subsequent merger, TD Ameritrade was established. (I opened a Datek account, later acquired by Ameritrade.)

In the mid-80s, I opened a Quick & Reilly account (actually two, one a regular account and one an IRA). Q&R was later acquired by FleetBoston, which was gobbled up by Bank of America. I closed the regular account and now have just the Roth IRA (after conversion) with B of A, which charges variable commissions; I have enough in it to get the $7 commission rate.

FWIW, the best known U.S. discounters now are probably TD Ameritrade and E*Trade, with commissions in the $9-10 range. I think that Scottrade and TradeKing may be in the $5-7 range(?) and then there's Zecco at Zero commissions. Wells Fargo and Bank of America also offer zero commissions if you meet certain asset levels.