Twenty years to the day after shares of CoBiz Financial first started trading, chairman and CEO Steven Bangert announced an agreement to sell the company he shepherded for just shy of $1 billion.

The initial ante he and banker Scott Wylie raised in 1994 to purchase Equitable Bankshares — owner of the Women’s Bank of Denver, predecessor of Colorado Business Bank — was $17.5 million.

Tulsa-based BOK Financial Corporation has agreed to pay $977 million to acquire Denver-based CoBiz Financial Inc., the two companies said on Monday.

BOK Financial already owns Colorado State Bank and Trust and plans to combine the two financial service firms to create a bulkier competitor with control of about 4.2 percent of Denver’s banking market.

“They will combine operations,” confirmed Kent Sholars, a spokesman for BOK, adding a decision hasn’t been made yet on which name or brand BOK Financial will go with in Colorado.

CoBiz counts $3.8 billion in assets and $3.2 billion in deposits, of which $1.9 billion are based in Colorado. The company employs 538 people and runs 15 branches in Colorado and Arizona. Colorado State Bank and Trust has $1.5 billion in deposits.

About 75 percent of the purchase price will come in the form of BOK stock, with the remainder in cash. Shares of CoBiz Financial fell 1.2 percent Monday to close at $21.88 a share, which resulted in a market value of $927.5 million. BOK has offered $23.02 a share for CoBiz’s stock.

After the purchase of Equitable Bankshares in 1994, Bangert took what was the Women’s Bank of Denver, one of the first nationally chartered banks focused on serving women, and broadened its mission and customer base.

He took the holding company public in 1998 and used the stock to purchase several local financial service firms including Milek Insurance Services, investment bank Green Manning & Bunch, Alexander Capital Management and Financial Designs Ltd. CoBiz also acquired an Arizona bank and set up operations in that state.

Bangert, CoBiz’s chairman and CEO, will join BOK Financial’s board of directors.