From Then (1846):

A computer scan of a photograph of the Bear Flag Rebellion flag of 1846.

"According to the California Blue Book:
"The flag was designed by William Todd on a piece of new unbleached cotton. The star imitated the lone star of Texas. A grizzly bear represented the many bears seen in the state. The word, "California Republic" was placed beneath the star and bear. ..." "

[The "Lone Star" flag is also the "Bonnie Blue" flag and both flags show a White star upon a Blue field:]

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[I'm not going to duplicate this site, so go visit:]
The San Francisco Museum: The California Bear Flag.

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To Now (1999):

The "official" flag of THE STATE OF CALIFORNIA today.

West's ANNOTATED CALIFORNIA CODES, GOVERNMENT CODE (1998), Section 420:

The Bear Flag is the State Flag of California. As viewed with the hoist end of the flag to the left of the observer there appears in the upper left-hand corner of a white field a five-pointed red star with one point vertically upward and in the middle of the white field a brown grizzly bear walking toward the left with all four paws on a green grass plot, with head and eye turned slightly toward the observer; a red stripe forms the length of the flag at the bottom, and between the grass plot and the red stripe appear the words CALIFORNIA REPUBLIC.
Dimensions, excluding heading and unfinished flag ends: The hoist or flag width is two-thirds of the fly or flag length; the red stripe width is one-sixth of the hoist width. The state official flag hoist widths shall be two, three, four, five, six and eight feet. The diameter of an imaginary circle passing through the points of the star is one-tenth of the fly length; the distance of the star center from the hoist end is one-sixth of the fly length and the distance of the star center to the top of the flag is four-fifths of the star-center distance from the hoist end. The length of the bear diagonally from the nose tip to the rear of the right hind paw is two-thirds of the hoist width; the height of the bear from shoulder tip vertically to a line touching the bottoms of the front paws is one-half the length of the bear; the location of the bear in the white field is such that the center of the eye is midway between the top and the bottom of the white field and the midpoint of the bear's length is midway between the fly ends. The grass plot in length is eleven-twelfths of the hoist width and the plot ends are equidistant from the fly ends; the average width of the the plot between the rear of the left front paw and the front of the right rear paw is one-tenth of the grass plot length. The height of the condensed gothic letters, as shown on the representation, is one-half of the red stripe width and they occupy a lineal space of two-thirds of the fly length with the beginning and ending letters of the words equidistant from the fly ends.

West's ANNOTATED CALIFORNIA CODES (1998), MILITARY AND VETERAN'S CODE, Section 611:

(a) "Flag," as used in this division means the State Flag of California and the Flag of the United States, as defined in this section.
(b) "State Flag of California" includes any flag, standard [cavalry], color [Army], or ensign [Navy] authorized by the laws of this state, and every picture or representation thereof, of any size, made of any substance, or represented on any substance evidently purporting to be any such flag, standard, color, or ensign of this state, and every picture or representation which shows the design thereof.
(c) "Flag of the United States" includes any flag, standard, colors, or ensign authorized by the laws of the United States or any picture or representation of either[?], or of a part or parts of either, made of any substance or represented on any substance, of any size evidently purporting to be either of said flag, standard, colors, or ensign of the United States of America, or a picture or a representation of either, upon which shall be shown the colors, the stars and the stripes, in any number of either thereof, or of any part or parts of either, by which the average person seeing the same without deliberation may believe the same to represent the flag, standards, colors, or ensign of the United States of America.

[Now, this definition sounds to me like someone just created the "justification" to display bogus or not-quite-legitimate flags while hoping we won't notice. If something is "evidently purporting" to be something else, by the definition of "purport", it is not the thing it is "evidently purporting" to be. [Why would anyone legitimately wish me to "believe" that I am viewing "without deliberation" the flag of the United States of America or the flag of California if I am not?
[More importantly if I am not viewing the flag of the United States of America or the flag of the State of California, exactly what flag am I viewing?]

[So I went back through the bound volumes of California Statutes and Amendments to the Codes to see what I could find.]

[The first thing which amazed me was that there does not seem to have been any legal definition of the California state flag prior to 1911.]
[Of course that may not have been so unusual considering that the state flag supposedly burned in the San Francisco earthquake in 1906.
[How the flag got into the San Francisco Museum, I do not know.
[Before 1906, if you wanted to see the state flag, you went to the State Capitol or the San Francisco Museum and voila ... there it was.]

[Anyway, by 1911, the Legislature had passed the first California flag law:]

California Satutes and Amendments to the Codes (1911), c. 9, p. 6:

An act to select and adopt the bear flag as the state flag of California. [Approved February 3,1911.]"
Section 1. The bear flag is hereby selected and adopted as the state flag of California.
Sec. 2. The said bear flag shall consist of a flag of a length equal to one and one half the width thereof; the upper five sixths of the width thereof to be a white field, and the lower sixth of the width thereof to be a red stripe; there shall appear in the white field in the upper left hand corner a single red star, and at the bottom of the white field the words "California Republic," and in the center of the white field a California grizzly bear upon a grass plat, in the position of walking towards the left of the said field; said bear shall be dark brown in color, and in length equal to one third of the length of said flag.
Sec. 3. This act shall be in full force and effect from and after its passage.

[There are legal distinctions between "plat" and "plot". Research them in a legal Dictionary like BLACK'S LAW DICTIONARY.]

[This was followed by the adoption of the Military Code in 1933.]
California Statutes and Amendments to the Codes (1933), ch. 975, p. 2501:

91. State Flag. The Bear flag is hereby selected and adopted as the State flag of California. Its length shall be one and one-half times its width; the upper five-sixths of the width thereof shall be a white field and the lower sixth a red stripe; there shall appear in the white field in the upper left-hand corner a single red star, and at the bottom of the white field the words "California Republic," and in the center of the white field a California grizzly bear upon a grass plat, in the position of walking towards the left of the said field; said bear to be dark brown in color and in length, equal to one-third of said flag.

92. Definition of Flag. "Flag," as used in this code, includes every flag, standard, color, or ensign authorized by the laws of the United States or of this State, and every picture or representation thereof, of any size, made of any substance, or represented on any substance evidently purporting to be any such flag, standard, color or ensign of the United States or of this State, and every picture or representation which shows the design thereof.

610. The bear flag is the State flag of California. Its length is one and one-half times its width; the upper five-sixths of the width thereof is a white field and the lower sixth a red stripe; there apperars in the white field in the upper lefthand corner a single red star, and at the bottom of the white field the words "California Republic," and in the center of the white field a California grizzly bear upon a grass plat,in the position of walking towards the left of the white field, the bear is dark brown in color and its length one-third of the length of the flag.

611. "Flag" as used in this division, includes every flag, standard, color, or ensign authorized by the laws of the United States or of this State, and every picture or representation thereof, of any size, made of any substance, or represented on any substance evidently purporting to be any such flag, standard, color,or ensign of the United States or of this State, and every picture or representation which shows the design thereof.

[Isn't that odd?]