Knuth, The Early Development of Programming Languages, originally published in Encyclopedia of Computer Science and Technology (1977) and reprinted in Selected Papers on Computer Languages gives information on early languages (including the implementation a small program) and is probably the best accessible source on them.
The earlier he cites is Plankalkül (Zuse, 1945), which wasn't implemented and the describing paper not even published before 1972) thus had little influence.
Then he gives Flow Diagrams (Goldstine and von Neumann, 1946), Composition (Curry, 1948), Short Code (Mauchly et al., 1949), Intermediate PL (Burks, 1950) and some later one.
Sammet, Programming Languages: History and Fundamentals is little concerned by "early languages", but gives a list of about 150 languages from before 1959.
FORTRAN is probably the earliest one still existing and having lot of influence. COBOL, LISP are also still existing and -- for LISP -- a lot of variants and descendants. ALGOL is probably the major influencing programming languages which hasn't evolved in direct line until now -- but it has lot of presence, C being one of its indirect descendant.