In the Financial District, two financial firms — one women-owned, the other minority-owned — are merging and expanding.

Now the nation’s No. 1 women-owned and minority-owned investment bank — rebranded as Siebert Williams Shank & Co. — is the result of the merger between the women-owned public finance firm Siebert Cisneros Shank & Co. and minority-owned corporate financiers The Williams Capital Group.

When the two officially merge in November, it will occupy the entire 19,650-square-foot 18th floor at 100 Wall St., which is a 520,000-square-foot Class A office building on the northwest corner of Water Street. The expansion will increase the size of the sales and trading desk area.

Eric S. Yarbro of Colliers International, who has represented Siebert for the last decade, repped the firm in the new 10-year expansion and in its last two. In all three cases, Yarbro also shared his own Rolodex — leading to the selection of the architect, contractor, HVAC companies and others involved in the design and construction of the space — enabling it to exceed their own minority-procurement goals.

Scott D. Cahaly of JLL represented the Cornerstone Real Estate Advisers ownership.