MidFirst Bank chairman and CEO Jeff Records said: "This acquisition provides MidFirst a great entry into the dynamic Denver market.
"We are very excited to align ourselves with the Steele Street team. Thanks to the talented professionals that built this very successful institution, we are confident we can continue the momentum and deliver enhanced products and services to our clients in Colorado."
Steele Street chairman and CEO Bob Malone said: "MidFirst’s ownership has deep roots in Colorado, and they share our passion for genuine community banking.
"As part of MidFirst Bank, we will be able to offer clients a wider array of products and will be able to serve them through all stages of their growth."
As of 31 December 2014 Steele Street Bank & Trust had assets totaling $572m, deposits of $512m, and wealth management relationships of more than $1bn.
MidFirst Bank is headquartered in Oklahoma City and has total assets of $9.5bn.
