He communicated his botanical results with the three top American botanists of the day, John Torrey, Asa Gray, and George Engelmann.

He took up teaching to gain the funds to attend the Medical College of Ohio in Cincinnati, from which he graduated with an MD degree in 1832.

[10] In his early years, in addition to establishing a medical practice,[1] he spent much time becoming familiar with the flora of central Ohio, joining with other local physicians and William Starling Sullivant, a prominent botanist residing in the area.

[1] Sullivant specialized in the study of bryophytes, but had broad botanical interests, and was in close contact with John Torrey and Asa Gray.

In an 1841 presentation to the Medical Convention of Ohio (see Works, 1841) he stated that Botany was the most important science "collateral to medicine", but that most members of the profession were "careless" or "indifferent" regarding it.

In 1850 (following some early confusion[1]), Bigelow joined the Mexican Boundary Survey to serve as both surgeon and botanist on the expedition led by Major William H. Emory.

[14] Bigelow joined the Pacific Railroad Survey which explored along the 35th parallel, led by Lt. Amiel Weeks Whipple.

In his diary of the expedition (including a preface by his mentor Alexander von Humboldt), Möllhausen records many of their exploits.

[15] On March 24 most members of the expedition left Los Angeles for San Francisco, where they would take a steamer to Panama, and thence back to Washington, D.C.[15] Because of the season though, so conducive to growth and bloom of native plants, Bigelow decided to remain and botanize this mid-section of California, a state only recently admitted to the US.

[17] Torrey stated that Bigelow's collections were "brought home in perfect order" affording "abundant proof of the zeal and success with which he labored.

A number of new genera, and more than sixty new species, have been discovered by Dr. Bigelow, and he has added much valuable information upon many heretofore imperfectly known plants.

"[16] After the report had been completed and the authors dispersed, Möllhausen wrote in his diary[15] (vol 2, p 388) "Whether I may ever again meet with any of my old comrades seems uncertain, for our merry party has been scattered to all points of the compass.

My dear and worthy friend Dr. Bigelow is now living happily in his family circle in Ohio and employing his leisure hours in botanising excursions about the country .

In 1860 "Bigelow was placed in charge of the meteorological division" of the United States Lake Survey, a position he retained until January 1, 1867.

";[5] "He always impressed me by his singular modesty, never permitting his attainments to obtrude themselves in a pretentious way, while his uprightness and meekness of manner gave to him that attractiveness which arrested the attention of those who were at all acquainted with him.

"; "The modesty that graced his every act, the tender and delicate feeling that smoothed and made delightful his intercourse with his professional brethren, shall ever endear him in our memory.