The Historic Oklahoma Natural Gas Company building, now known as the 624 Boston Building, was purchased by the Hille Foundation in 2007 to provide offices for the foundation and to operate as an office building. The building was built in 1928 by Frank Phillips, of Phillips Petroleum, to house Oklahoma Natural Gas Company (ONG), which he purchased and moved to Tulsa from Oklahoma City. The Oklahoma Natural Gas Company Building was one of the first Art Deco buildings built in Tulsa. The selection of this style by a generally conservative utility company established its acceptance and paved the way for a host of Art Deco buildings which were to follow. The Building is constructed of reinforced concrete, enclosed with buff tapestry brick and trimmed with Indiana limestone and vitreous tile. The materials and designs in the interior of the building are a significant feature of the Zig-Zag Art Deco style. The building continues to be a viable part of downtown Tulsa and provides a visible and tangible link to an important period in its past.