Tuesday morning, the two held a "ribbon-tying ceremony" at the former Tri-City Jewish Center in Rock Island.
Library Director Angela Campbell says both organizations considered the center for future expansion, but could not afford it alone. Then they decided to work together.
"Our partnership has allowed us to offer everything that people wanted in a branch - a large community room, internet connectivity, popular materials, conference rooms, teen area, study rooms, outdoor space - for a fraction of the cost of doing the project alone."
Now everyone in Rock Island will be within three miles of a public library.
Two Rivers CEO Mike Wennekamp says once they decided to work together, feasibility studies showed the community would support a joint facility.
"400 donors, a ton of volunteers, and about 8 1/2 million dollars in donations, and here we are."
Library board member and 4th Ward Alderman Jenni Swanson says this is one of only three YMCA-library joint facilities in the country.
The Y will officially open on Thursday, and the library will open the new Watts-Midtown Branch next Monday (2/13).
