‘Abdu’l-Bahá elaborates on the significance of the 12 Central States, the Heart of America

These twelve Central States [1] of the United States are like unto the heart of America, and the heart is connected with all the organs and parts of man. If the heart is strengthened, all the organs of the body are reinforced, and if the heart is weak all the physical elements are subjected to feebleness.

Now praise be to God that Chicago and its environs from the beginning of the diffusion of the fragrances of God have been a strong heart. Therefore, through divine bounty and providence it has become confirmed in certain great matters.

First: The call of the Kingdom was in the very beginning raised from Chicago. This is indeed a great privilege, for in future centuries and cycles, it will be as an axis around which the honor of Chicago will revolve.

Second: A number of souls with the utmost firmness and steadfastness arose in that blessed spot in the promotion of the Word of God and even to the present moment, having purified and sanctified the heart from every thought, they are occupied with the promulgation of the teachings of God. Hence the call of praise is raised uninterruptedly from the Supreme Concourse.

Third: During the American journey ‘Abdu’l-Bahá several times passed through Chicago and associated with the friends of God. For some time he sojourned in that city. Day and night he was occupied with the mention of the True One and summoned the people to the Kingdom of God.

Fourth: Up to the present time, every movement initiated in Chicago, its effect was spread to all parts and to all directions, just as everything that appears in and manifests from the heart influences all the organs and limbs of the body.

Fifth: The first Mashriqu’l-Adhkár in America was instituted in Chicago, and this honor and distinction is infinite in value. Out of this Mashriqu’l-Adhkár, without doubt, thousands of Mashriqu’l-Adhkárs will be born.

Likewise (were instituted in Chicago) the general Annual Conventions, the foundation of the Star of the West, the Publishing Society for the publication of books and Tablets and their circulation in all parts of America, and the preparations now under way for the celebration of the Golden Centenary Anniversary of the Kingdom of God. 

- ‘Abdu’l-Baha  (‘Tablets of the Divine Plan’)

[1] “Michigan, Wisconsin, Illinois, Indiana, Ohio, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska and Kansas.”