In 1859, Western Union standardized on the "92 code"

In 1859, Western Union standardized on the "92 code" in which the numbers from 1 to 92 were assigned meanings. It was in this list that 73 got its present meaning. Later more numbers were added. Here's a partial list:

1 Wait a moment 
2 Important Business 
3 What time is it? 
4 Where shall I go ahead? 
5 Have you business for me? 
6 I am ready 
7 Are you ready? 
8 Close your key; circuit is busy 
9 Close your key for priority business (Wire chief, dispatcher, etc)
10 Keep this circuit closed 
12 Do you understand? 
13 I understand 
14 What is the weather? 
15 For you and other to copy 
17 Lightning here 
18 What is the trouble? 
19 Form 19 train order 
21 Stop for a meal 
22 Wire test 
23 All copy 
24 Repeat this back 
25 Busy on another wire 
26 Put on ground wire 
27 Priority, very important 
28 Do you get my writing? 
29 Private, deliver in sealed envelope 
30 No more (end) 
31 Form 31 train order 
32 I understand that I am to ... 
33 Car report (Also, answer is paid for) 
34 Message for all officers 
35 You may use my signal to answer this 
37 Diversion (Also, inform all interested) 
39 Important, with priority on thru wire (Also, sleep-car report) 
44 Answer promptly by wire 
73 Best regards 
88 Love and kisses 
91 Superintendent's signal 
92 Deliver promptly 
93 Vice President and General Manager's signals 
95 President's signal 
134 Who is at the key?