I don't think Objective C was in use from the beginning of Apple hardware development. What languages did app developers use for the earlier Apple computers, such as Apple II or Mac Classic?
In 1985 Larry Tesler developed a Pascal flavour for Apple, Object Pascal, that became the standard language for System 6. It was based on Clascal, a 1983 Pascal variant for the Lisa, also developed at Apple.
Object Pascal was used in MacApp, Apple's primary application framework at the time. MacApp 3.0, released in 1991, was re-written in C++ and Apple subsequently dropped support for Object Pascal in favour of C++ when they moved from Motorola's 68K chips to PowerPC.
Borland's Object Pascal, that today lives on as Embarcadero Delphi, started out in 1986 as a set of extensions to Turbo Pascal, that were intended to be similar to Apple's Object Pascal. Niklaus Wirth, Pascal's originator, was consulted by both Apple and Borland for their respective variants.
Conversely, Objective C was NeXTSTEP's main language and was introduced at Apple only after they purchased NeXT in 1996.
The Apple ][ was generally programmed in either BASIC or 6502 machine code.
The Lisa was generally programmed in Pascal.
Early Macintosh apps were written in Pascal, first on the Lisa and later on the Mac itself.
Think Pascal was the most popular development environment for a time and then Think C. Think C had lightweight objects, sometimes referred to as C+-, and later C++. It also had its own class library called, appropriately enough, the Think Class Library.
MPW from Apple was also popular since it allowed you to mix languages (generally Pascal, C, C++, and assembler) and script builds similar to a unix environment, though the syntax was very different.
MacApp was written in Object Pascal, and as someone said, later moved to C++. With the move to PowerPC systems, many programmers switched to Metrowerks CodeWarrior as a development environment and its C++ class library, PowerPlant.
Objective-C was used at NeXT and then for Mac OS X, although Mac OS X applications could also be written in C/C++ via Apple's "Carbon" API. These days most Mac and iOS apps are written in Cocoa/Obj-C, although many have C or C++ libraries underneath.
The standard language of Mac OS Classic was Pascal. The OS's API documentation was all written for Pascal, and as much of the OS as was not written in hand-optimized ASM was written in Pascal.
After transitioning to the PowerPC architecture, they rewrote the OS in C++, accompanied by a very noticeable decrease in system stability, which will not be surprising to anyone familiar with Pascal and C++. API documentation continued to be written primarily for Pascal, though, until Steve Jobs came back and started trying to force Objective-C down everyone's throats.