I'm writing a story with some scenes taking place in 1851 on a train
between Philadelphia and Baltimore.

I'm looking for the following information:
1. What was/were the names of the railroad(s) from Philadelphia to Baltimore?
2. How many classes of travel were there?
3. What was the price of the lowest class ticket?
4. Are there any photographs of the inside of the railway cars?
5. How many stops were there?

Thank you very much for your help!

Hi querious~

I am not posting this as an Answer, because it doesn?t address all
your questions. If it meets your needs and you wish me to post it as
an Answer, just let me know. Otherwise, I hope it helps some.

The Railroad in the early- to mid-19th century was an uncomfortable
ride, indeed. Passengers complained about derailments, boiler
explosions, incredible noise, livestock and wild animals being run
down, and ashes that fell down on them from the train?s smoke stacks.
Like today, passengers also complained about the ?baggage smashers?
who, judging from the way they handled luggage, seemed to hate the
sight of it.
According to ?Everyday Life in the 1800s? (see the Amazon listing
here: http://www.amazon.com/exec/obidos/tg/detail/-/1582970637/qid=1082652150/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/102-4441094-4616117?v=glance&s=books&n=507846
), ?One woman found 13 holes burned in her gown from the engine?s
relentless belching of sparks.?

By the 1850s, some trains were still heated with wood stoves found at
the end or the middle of each passenger car.

The first dining cars weren?t used until the 1860s. Instead, railway
lines established ?refreshment saloons? along routes; stops were not
infrequently as short as 15 minutes. There were a few sleeping cars as
early as the 1840s, but they weren?t widely popular until the 1860s.

Trains at around mid-century ran between 20 and 40 miles per hour.

I was unable to find actual fare prices for 1851, but this info might
help: According to ?Everyday Life in the Wild West? (see the Amazon
listing here: http://www.amazon.com/exec/obidos/tg/detail/-/1582972117/qid=1082652173/sr=1-1/ref=sr_1_1/102-4441094-4616117?v=glance&s=books),
?The Union Pacific/General Pacific line started passenger service on
May 15, 1869. The fare was $100 for first class service from Omaha to
Sacramento; for an extra $4 first-class passengers could obtain meal
service on the train; otherwise they ate at stops along the way.
Second-class passengers rode and slept in day coaches and paid $80 for
a ticket from Omaha to Sacramento. Third-class passengers, primarily
emigrants, traveled in cars fitted with narrow wooden benches in rows.
They paid $40 for an Omaha-to-Sacramento ticket. The cars with
emigrants were often attached to freight trains and were stopped for
other trains to pass; therefore, it might take an emigrant ten days to
make the same trip a first-class passenger could make in four days.?

Regards,
Kriswrite

Kriswrite-
Thanks for your research.   It answers most of my questions - why
don't you post it as an answer?  Can I then ask for more responses?
Best,
Querious!

Hi querious~

Thank you for suggesting I post my comment as an Answer. However, if I
do so, you'll be able to solicit more information through comments
only. (Or, by posting another question.) Let me know if that works for
you :)

Kriswrite