Minneapolis investment bank Piper Jaffray Cos. (NYSE: PJC) has closed a $21 million deal for Seattle-Northwest Securities Corp.

Seattle-Northwest, founded in 1970, underwrites municipal securities.

Piper Jaffray says the deal strengthens its public finance franchise and its ability to serve municipal and middle market clients.

In June, Piper Jaffray announced it was buying investment bank Edgeview Partners LP, which provides middle-market M&A advisory services.