WASHINGTON » As he embarks on his final years in office, President Barack Obama has begun to look beyond the White House to his next task: solidifying his legacy.

A group of longtime friends and supporters, including his former campaign manager and fundraiser, is in the midst of planning a multimillion-dollar presidential library that will house enough unclassified documents to fill four 18-wheelers and enough artifacts to fill a swimming pool.

In the coming months, Obama will decide whether to build the library in one of the cities he once called home or, perhaps, the place he’s considering calling home after he leaves 1600 Pennsylvania Ave.: Hono­lulu, Chicago or New York.

"Each president shapes his presidential library around his own interests," said James Rutherford, dean of the Clinton School of Public Service at the University of Arkansas, who was influential in the creation of the William J. Clinton Presidential Library and Museum in Little Rock. "The president really is the determining factor into where a presidential library will go and what its mission will be."

The Barack Obama Foundation expects to narrow possible locations by late summer. The president and first lady will select the site early next year. Thirteen organizations submitted proposals to build a facility that will be much more than a library — part museum, part education center and part archive. There will be a gift store and restaurant as well.

At least five are in Illinois, where Obama launched his political career, and one each in Hawaii, his birth state, and New York, where he graduated from college. Illinois is thought to be the front-runner, though Hawaii has been lobbying for the library for years.

"It has been said that to understand where you are going, you must understand where you are from," Chicago State University President Wayne Watson said. "President Barack Obama is from many places. He was born in Hawaii and lived in diverse locations throughout his childhood. He was educated on the East Coast. Yet without a doubt, Barack Obama the leader was born into political action on the Far South Side of Chicago."

Despite a commitment to what the library foundation calls "transparency and fairness," some of the proposals remain shrouded in secrecy. The foundation has declined to release them, and only some of the potential developers have announced their interest. Many didn’t return calls to answer further questions.

Foundation officials, however, say they have rejected a proposal from a university in Kenya — where Obama’s father was born and where his half sister, Auma, lives — for the Barack Obama Institute for Peace and Democracy Studies in Nairobi, because it was "not responsive to the guidelines."

Obama has indicated he wants his library to be an anchor for economic development while reflecting the values of his public-service career: expanding economic opportunity and promoting peace, justice and dignity around the world.

A pair of studies conducted in Chicago and Hono­lulu estimates a library could generate hundreds of millions of dollars annually, create nearly 2,000 permanent jobs and lure up to 800,000 visitors each year.

Thirteen presidential libraries are scattered across the nation. Ronald Reagan’s library in Simi Valley, Calif., is the most popular, with about 400,000 visitors annually. But Obama’s could very well surpass that because of his historic tenure as the first African-American U.S. president.

A 70-page document released by the foundation outlines what the library will house, according to the National Archives and Records Administration: more than 20,000 cubic feet of unclassified documents, 15,000 cubic feet of artifacts, 5,676 cubic feet of classified documents and 804 cubic feet of audiovisual records.

"The president’s future library will one day serve as an important part of our nation’s historical record, and our mission is to build a library that tells President Obama’s remarkable story in an interactive way that will inspire future generations to become involved in public service," said Martin Nesbitt, a longtime friend and golf partner of Obama’s who agreed to serve as foundation board chairman.

Donations will pay for the construction, but the federal government will maintain the facility. The state and local government may choose to contribute. Wealthy supporters have so far donated a total of $850,000 to $1.75 million. The foundation has pledged to release names of those who gave more than $200 on its website on a quarterly basis, though only with donation ranges.

The donors — all from Chicago and New York — either raised money for Obama during one of his campaigns or were appointed by him to various boards. The Obamas and their staff pledged not to raise money for the library while in office.

Chicago officials argue the library should be in their city, where Obama served as a community organizer and state senator. He taught at the University of Chicago while Michelle Obama worked at its hospital. Their daughters, Malia and Sasha, attended the University of Chicago Laboratory Schools.

At least five bids are from Chicago: the University of Chicago, the University of Illinois at Chicago, Chicago State University, developer Dan McCaffery, and the President Obama Library and Museum Campus Foundation, a community-based organization.

"Such a location would reflect the personal and professional lives of the Obamas as well as their commitments to society," University of Chicago President Robert Zimmer said.

Hawaii is offering an oceanfront site. Perhaps realizing the Windy City may have the edge, the University of Hawaii has agreed to partner with another site to create an institution with two campuses.

"Our global orientation, multicultural population, robust visitor industry and unrivaled natural beauty make Hawaii a logical destination to house and nurture the president’s legacy," Hawaii Lt. Gov. Shan Tsu­tsui said.

New York was Obama’s home during college and for a brief time after he graduated from Columbia University with an undergraduate degree in political science.

"We believe Columbia and New York City would provide a fitting platform for a post-presidency engaged in the vital issues of our time, while further adding to our core mission of teaching, research and public service," Columbia said in a statement.

Anita Kumar, McClatchy Washington Bureau