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BlackRock Municipal Bond Fund, Inc. – BlackRock Impact Municipal Fund

Post-Effective Amendment No. 70 under the Securities Act of 1933

and Amendment No. 68 under the Investment Company Act of 1940

to the Registration Statement on Form N-1A

(File Nos. 002-57354 and 811-02688)                                                                 

With respect to the subsection in the Fund’s Prospectuses entitled “Fund Overview – Key Facts About BlackRock Impact Municipal Fund – Fees and Expenses of the Fund,” please provide the completed fee tables and expense examples at least one week prior to effectiveness of the Amendment.

The completed fee tables and expense examples were provided supplementally to the Staff via email on March 3, 2022.

The Staff believes that the use of the word “Impact” in the Fund’s name suggests a type of investment, and therefore the Fund should include an 80% names rule policy that covers “Impact.”

The Fund respectfully disagrees with the Staff’s position with respect to the applicability of Rule 35d-1 (the “Names Rule”) to the use of the term “Impact” in the Fund’s name. The Fund notes that the Names Rule requires that a fund with a name that suggests that the fund focuses its investments in a particular type of investment or industry adopt a policy to invest, under normal circumstances, at least 80% of its net assets in the particular type of investment or industry suggested by the fund’s name. However, in the release adopting the Names Rule (the “Adopting Release”) and the companion release to the Adopting Release, titled “Frequently Asked Questions about Rule 35d-1 (Investment Company Names),” the Staff distinguished terms that suggest an investment objective or strategy, rather than a type of investment, and noted that such terms do not require adoption of an 80% policy pursuant to the Names Rule.¹ The Fund believes that the word “Impact” in the Fund’s name does not suggest a “particular type of investment” subject to the Names Rule, but rather that it reflects the investment process and philosophy utilized by BlackRock in selecting investments for the Fund.

Please confirm that derivatives will be marked-to-market for purposes of the Fund’s 80% investment policy.

The Fund confirms that under normal circumstances it intends to value derivatives using the marked-to-market value for purposes of meeting its 80% investment policy.

See Investment Company Names, Investment Company Act Rel. No. 24828 (Jan. 17, 2001); see also Question #9 in Frequently Asked Questions about Rule 35d-1 (Investment Company Names), available at: https://www.sec.gov/divisions/investment/guidance/rule35d-1faq.htm (“[T]he term ‘growth and income’ does not suggest that a fund focuses its investments in a particular type of investment, but rather suggests that a fund invests its assets in order to achieve both growth of capital and current income”).

The Staff had the following comments relating to the Fund’s impact strategy:

The disclosure notes that the Fund intends to focus on investments in education, healthcare, housing, water and sewer, low carbon public power issues and mass transit. What positive and measurable impacts is the Fund seeking to achieve in these areas? Without additional clarity, we do not believe that investors will be able to tell which impacts the Fund is seeking to achieve.

The Fund has considered the Staff’s comment and will make the following revisions to its prospectus disclosure to provide additional clarity to investors (additions underlined; deletions in strikethrough):

Please disclose how the Fund will measure whether its investments are “generat[ing] positive, measurable social and environmental impact.”

Please see Response No. 4a above regarding additional disclosure in response to this comment.

Please disclose whether and where the Fund will tell investors whether these impacts are being achieved.

As disclosed in the prospectus, Fund management applies a proprietary framework to measure the impact of the Fund’s investments. BlackRock plans to make certain reports related to the Fund’s impact metrics and outcomes available to investors on the BlackRock website once the Fund has established an operating history and will continue to evaluate methods to share information regarding achievement of the Fund’s impact objectives with investors. BlackRock respectfully submits that information regarding such supplemental reporting is not required to be included in a fund’s prospectus.

Please disclose whether the stated impacts are prioritized over returns, treated the same as returns, or are secondary to returns.

The Fund confirms that, in seeking to achieve the Fund’s investment objective of maximizing income exempt from Federal income taxes while investing (emphasis added) in municipal bonds the proceeds of which Fund management views as generating positive social and environmental impacts, Fund management does not expect to prioritize returns over the stated impacts, or the stated impacts over returns. Rather, Fund management generally views the goals of generating investment returns and seeking to achieve the stated impacts as complementary. The Fund acknowledges, however, that the Fund’s pursuit of the stated impacts may affect returns, and notes that this risk will be disclosed to investors. Specifically, the prospectuses currently disclose that “[t]he Fund may forego opportunities to buy or sell certain investments based on its selection criteria, which may affect the Fund’s exposure to those investments. As a result, the Fund’s results may be lower than other funds that do not seek to invest based on expected impact outcomes.”

The Staff believes it would be more beneficial if the Fund’s principal risks are reordered based on the level of risk, with the most significant risks to the Fund listed first. We note that the former Director of the Division of Investment Management has addressed the practice of some funds of listing risk factors in alphabetical order. See https://www.sec.gov/news/speech/speech-blass-102518.

The Fund has considered the Staff’s comment and will reorder its principal risk factors in the Amendment such that several risk factors that the Fund currently considers more significant will be listed at the beginning of the applicable sections of the Fund’s prospectuses. The Fund will continue to consider the ordering of its risk factors.

In the sub-section entitled “Fund Overview—Principal Risks of Investing in the Fund—Debt Securities Risk—Interest Rate Risk,” the disclosure introduces the term “duration.” Please briefly explain that duration is a measure of the price sensitivity of a debt security or portfolio of debt securities to relative changes in interest rates.

The Fund will make the following revisions to the “Interest Rate Risk” disclosure in the applicable sections of the Fund’s prospectuses:

Please note that the Fund should look through a private activity municipal debt security whose principal and interest payments are derived principally from the assets and revenues of a non-governmental entity in order to determine the industry to which the investments should be allocated when determining the Fund’s compliance with its concentration policy

The Fund confirms that it will look through a private activity municipal debt security whose principal and interest payments are derived principally from the assets and revenues of a nongovernmental entity in order to determine the industry to which the investments should be allocated when determining the Fund’s compliance with its concentration policy.

/s/ Michael A. DeNiro

Jessica A. Holly, Esq., BlackRock, Inc.

Elliot J. Gluck, Esq., Willkie Farr & Gallagher LLP