Certificates offer conclusive proof.

The "proven" category is the highest degree of confidence. To include a state in this category means that states are precisely known from certificates or they are very strongly implied from certificates.

State seals are excellent indications of incorporation, but...

State seals are not necessarily 100% inclusive. In other words, companies may have been incorporated in multiple states, not all of which are represented by state seals.

See examples of state seals

What about territories?

Many companies were organized in U.S. territories, prior to statehood. However, many certificates do NOT specifically say "Territory." Therefore, many territorial certificates are known but not identified as such. See state and country data dates of statehood. If I know companies were organized during territorial periods, I indicate such. But I have not caught all. (Hint: check Arizona and New Mexico certificates.)

City names can be misleading.

City names, either in company names or as locations of issuance, are strong implications of incorporation.

Unfortunately, they are sometimes very misleading. For instance, the US Safety Automatic Train Pipe Co of Washington DC was actually incorporated in Dallas, Texas!

State records prove incorporation...kinda

State records are definite proof of incorporation, but are sometimes very misleading. For instance, there may be huge numbers of tax and legal reasons why companies might incorporate in several states, but that is no proof that such companies actually operated there.

On the other hand, companies often incorporated in states where they had no operations and little on-the-ground presences to avoid certain state regulation where they conducted the bulk of their operations.

For instance, during the heydays of the large corporate trusts, many companies followed Standard Oil's lead and established offices in New Jersey. Through time, several states have served as corporate havens and tax sanctuaries, including Delaware, Maine, and Arizona. When such state names absolutely appear on certificates, then those names are bolded. Otherwise, they are relegated to secondary states of incorporation.

State records are not uniformly available, nor are they uniformly reliable.

Across the country, state records range from excellent to barely acceptable. Some states offer online access to historic records, but most do not. Some states require in-person research. Therefore, I call all secondary sources of information about states of incorporation "probable."

Overall, that means I am moderately confident of official incorporations in second-tier states. But, it also means I have not encountered any stocks or bonds that specifically list such names.

For instance, even though I "know" where the oldest New England railroads formed and operated, most of their stocks and bonds do NOT carry state names. Conversely, the majority of Texas issuances do list the Texas state name and/or they carry an implication of the Texas state seal (the "Texas star.")

California certificates often don't list the state name.

Nineteenth-century California stock certificates often carry the specific city and date of incorporation, but they seldom actually carry the California name. Hence, while I am 95% certain such companies were incorporated in the state of California, I cannot list them in the "proven" category.

Operations in multiple states.

Up until the era of the Transcontinental Railroad (the Union Pacific and Central Pacific), few companies incorporated in multiple states. A hundred years later, most track in North America is controlled by only a few, mostly conglomerate, mostly multi-state companies. Today the Union Pacific operates in 23 states, the BNSF in 25 states, the Norfolk Southern in 24 states, the CN in 21 states and provinces, and the CSX in 20 states.

It appears that most multi-state companies probably incorporated in some manner in the states they traversed. However, checking official records in all those states would be time-consuming, expensive, and far beyond the purpose of this project. Therefore, I relegate those inferred states of incorporation to the "states of operation" category. I will wait until readers give me more information.

HELP WANTED!

Please contact me when you have additional information to help refine my estimates on states of operation. See NEED STATES if you are a railfan and might know where companies operated.