Listed on the National Register of Historic Places in 1977, the Lilly Biological Laboratories in Greenfield, Indiana, stands as a highly significant monument to the evolution of the American pharmaceutical industry. Established in 1913 by Eli Lilly and Company, this sprawling campus was designed to isolate the delicate and highly sensitive production of biological medicines-such as vaccines and antitoxins-from the urban pollution of the company's downtown Indianapolis headquarters. The rural Hancock County site provided a controlled, sanitary environment where scientists and technicians could cultivate the animal serums required for early twentieth-century immunology, making it one of the earliest and most advanced industrial biological research and manufacturing facilities in the United States.

The historical significance of the laboratories lies in their profound contribution to global public health and medical science. It was at this facility that Eli Lilly and Company successfully standardized and mass-produced vital treatments, including diphtheria and tetanus antitoxins, smallpox vaccines, and later, the world's first commercially viable mass-produced insulin in the 1920s, which saved the lives of millions of diabetics worldwide. The campus reflects the critical transition of pharmacy from small-scale, empirical compounding to modern, scientifically rigorously controlled mass production, symbolizing a golden age of medical innovation and industrial research that reshaped twentieth-century healthcare.

The Lockheed PV-2 Harpoon No. 37396, located at the Indianapolis Regional Airport (formerly Mount Comfort Airport) in Hancock County, Indiana, is a exceptionally rare, surviving twin-engine maritime patrol bomber built for the United States Navy in 1945. Representing the final evolutionary design of the Lockheed Ventura series, the Harpoon was engineered specifically for long-range reconnaissance, patrol, and anti-submarine warfare during World War II. This aircraft is distinguished as one of only a handful of airworthy PV-2 Harpoons remaining in the world, serving as a highly intact, flying technological artifact that exemplifies mid-20th-century American military aviation engineering and manufacturing.

Listed on the National Register of Historic Places in 2009, the aircraft is significant for its association with United States military history and its outstanding engineering design. Delivered to the Navy in the closing months of World War II, this specific Harpoon later served in the Naval Air Reserve before being decommissioned. Its post-military career in the civilian sector as a corporate transport and an agricultural sprayer ultimately saved the airframe from the scrap yard. Acquired and meticulously restored to its original 1945 military configuration and livery by the Indiana Wing of the Commemorative Air Force, the aircraft serves as a premier educational resource and a flying testament to the naval aviation history and industrial home-front contributions of the World War II era.

The James Whitcomb Riley House, located in Greenfield, Indiana, holds profound historical significance as the birthplace and boyhood home of one of America's most celebrated late-nineteenth-century poets, James Whitcomb Riley, famously known as the "Hoosier Poet." Constructed primarily between 1850 and 1853 by the poet's father, Reuben A. Riley-a prominent local attorney, orator, and Civil War veteran-the two-story frame house originally incorporated the 1840s log cabin in which James was born in 1849. Featuring a blend of vernacular and Greek Revival architectural elements, the home reflects the modest, upwardly mobile lifestyle of a mid-nineteenth-century Midwestern family. It was within this domestic setting that Riley spent his formative childhood and adolescent years, absorbing the local dialects, folklore, and rural traditions that would later define his literary career.

The property is exceptionally significant under National Register Criterion B for its direct association with Riley, whose nostalgic, dialect-heavy poetry captured the imagination of a rapidly industrializing nation. Many of his most famous characters and poems were directly inspired by his life in this Greenfield home for instance, the beloved poem "Little Orphant Annie" was based on Mary Alice Smith, an orphaned child who came to live with the Riley family in this house, while "The Raggedy Man" drew from the family's hired hands. The "rafter room" in the home's attic served as a personal sanctuary where the young poet first began writing. Purchased by the James Whitcomb Riley Old Home Society in 1936 and opened as a museum in 1937, the house stands as an exceptionally preserved monument to the writer who permanently shaped the cultural identity of Indiana and American popular literature.