Mike Ramsey recently noted his hunch that state-constitutional analogues to the Speaker-of-the-House provision required that speakers of representative bodies be members. That inspired me to run through the 4562 pages of Thorpe's 1909 compilation of state constitutions (see here, here, here, here, here, here, and here to assemble your own) to see what might turn up.
For what it is worth, a few state-constitutional provisions mention the issue explicitly, but they first appear only with West Virginia in 1863. I use my idiosyncratic-but-concise way to refer to constitutional provisions, which I trust is clear. See 1875 Ala. IV/8 ("shall elect one of its members as speaker"), 1901 Ala. IV/51 (same), 1874 Ark. V/18 (speaker chosen "from its members"), 1876 Colo. V/10 ("one of its members"), 1897 Del. II/7 ("one of its members"), 1885 Fla. III/6 ("from among its own members"), 1865 Ga. II/3/3 ("shall be elected viva voce from their own body"), 1868 Ga. III/3/4 ("shall be elected viva voce from the body"), 1877 Ga. III/6/2 (same), 1889 Mont. V/9 ("one of its members"), 1889 ND II/36 ("one of its members"), 1873 Pa II/9 ("one of its members"), 1866 Tex. III/23 ("from their respective bodies"), 1868 Tex. III/29 (same), 1863 WVa IV/28 ("one of their own number"), 1872 WVa VI/24 ("from its own body"), 1889 Wyo III/10 ("one of its members"), 1907 Okla V/29 ("one of its members"). Several earlier state constitutions mention speakers pro tempore of the senate as senators. See 1818 Ill. IV/16 (when lieutenant governor acting as governor or unable to attend, senate elects "one of their own number" speaker), 1799 Ky. III/19 (same, "one of their own members"), 1850 Ky. III/18 (same). The Massachusetts "explanatory charter" of 1725 referred (as part of a long unnumbered ramble) to the assembly's power to "Elect a fit Person out of the said Representatives to be Speaker of the House of Representatives."
It is hard to know what to do with this evidence on its own. These explicit requirements may have been thought to restate a requirement implicit in the earlier rule that a house pick "its speaker," but they might also have been thought to impose a new requirement. From the sudden appearance of explicit requirements in the 1860s and 1870s, I imagine that the issue was probably first raised then, but without digging more into the history, it is hard to say much definitively. The prevalence of militarily-organized legislatures during the Civil War and Reconstruction may have precipitated newfound worry about legislative autonomy, but this is pure speculation.
Better evidence, perhaps, comes from provisions which assume, without requiring explicitly, that the speaker would be a member of the house. These provisions, which begin to appear at the founding, suggest that the term "speaker" implied membership in the house. 1776 Del. art. 7 it says in case of a tie vote for president, "the speaker of the council shall have an additional casting voice." 1792 Del. III/2 says in case of a tie vote, "the speaker of the senate shall have an additional casting vote." 1777 Ga. art. 28 refers to "the whole house at the time, except the speaker." 1889 NH art. 49 provides, "[W]hen the speaker of the House shall exercise the office of governor, he shall not hold his office in the House." 1902 NH art. 48 does the same. 1844 NJ IV/4/7 says, "The president of the senate and the speaker of the house of assembly shall, in virtue of their offices, receive an additional compensation, equal to one-third of their allowance as members." 1846 NY III/6 is similar: "The Speaker of the Assembly shall, in virtue of his office receive an additional compensation equal to one-third of his per diem allowance as a member." 1863 WVa IV/33 and 1872 WVa VI/33 likewise refer to "additional compensation" for the speaker beyond that for legislators, though as noted above, 1863 WVa IV/28 and 1872 WVa VI/24 make the house-membership requirement explicit.
As I see it–a similar view to Mike Rappaport's–the key question concerns the speaker's powers in coordinating the legislative powers of the House. Locke and the non-delegation doctrine tell us that the power to legislate is not the power to create legislators. If the speaker exercises part of the legislative power, he surely must be a member. The Sergeant at Arms and the like, by contrast, exercise no legislative power. But this possible limit on who may be speaker comes from the structural interaction of the "speaker" power, whatever that is, with "legislative" power, rather than from the speaker-appointing power in I/2/5 alone.
Added: Here is the entire discussion of the clause where an explicit speaker membership condition first appeared, from the West Virginia constitutional convention on January 7, 1862. (I take it from the excellent-but-expensive Making of Modern Law Primary Sources database; additional sections were apparently later added to the legislative article, changing it from section 22 to section 28.)
Posted at 9:00 AM